System for maintaining pH and sanitizing agent levels of water in a water feature

ABSTRACT

A system automatically maintains at least one of a pH level and a sanitizing agent level of water in a water feature. The system includes a sensor assembly responsive to at least one of a pH level of the water and a sanitizing agent level of the water. The system further includes a controller which generates control signals in response to signals from the sensor assembly. The system further includes at least one of a first source containing an sanitizing agent material and a second source containing a pH-modifying material. The system further includes a third source comprising a valve assembly and a third container containing a liquid calibrant material. The valve assembly is responsive to at least a portion of the control signals from the controller by selectively allowing the calibrant material to flow from the third container through the sensor assembly to the water feature.

CLAIM OF BENEFIT

This application claims the benefit of U.S. Provisional Application No.60/525,584, filed Nov. 25, 2003, which is incorporated in its entiretyby reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application relates generally to water maintenance systemsfor a water feature, and more specifically, to an automated watermaintenance system.

2. Description of the Related Art

Balancing the water chemistry (e.g., pH levels and sanitizing agentlevels) in water features (e.g., spas or swimming pools) can be achallenging and expensive operation. In particular, “balancing thewater” in a spa can be much more challenging than in a pool due to therelatively small volume of water in spas. The number of people per unitvolume of water is typically much higher in a spa than in a pool. Forexample, four people in a 300-gallon spa are comparable to 150 people inan average swimming pool. Because the water chemistry is affected by thefrequency of use and the number of bathers, maintaining the waterchemistry in spas can require more diligence to maintain than in pools.

Because of the relatively small volume of water in spas, users havesignificant difficulty in adjusting the pH level using highlyconcentrated pH-modifying materials, such as acidic materials (e.g.,sodium bisulfate) or alkaline materials (e.g., sodium carbonate). Inaddition, the effects of the acidity or alkalinity of other chemicals,which are added in considerable volumes to sanitize the water, must beaddressed in adjusting the pH level. For example, devices such aschlorine or bromine generators tend to increase the pH of the water as abyproduct of the chlorine or bromine generation. Excessive pH levels,either acidic or alkaline, will generally remain in the water untilcorrected. The persistence of low or high pH levels can cause orcontribute to corrosion of metal components of the heater and to scalingof the heater. In addition, because sanitizing agents such as chlorineare less efficient at high pH levels, improper pH levels can lead tounsanitary conditions.

Control of the sanitizing agent (e.g., chlorine or bromine) to ensurethat a spa is sanitary is similarly difficult and expensive. Existingsystems require operator monitoring and intervention to deal withdeviations or low levels of the sanitizing agent. For example, in spasand swimming pools, simple floating dispensers are often used. Suchdispensers must be adjusted to a proper feed rate and require attentionover a period of days. Variations of the frequency of use of the waterfeature by bathers or other system parameters can render such devicesuseless and can require supplemental addition of sanitizing agents tothe water. There is a certain forgiveness with the addition of excesssanitizing agent, since excess levels will eventually dissipate or willotherwise be consumed. However, an overfeed condition in which too muchsanitizing agent is used can result in corrosion of metal components ofthe water feature in general, and in the heater in particular.

Manual control of the pH level typically requires the user to test thewater at regular intervals using a test kit or test strip and then to“adjust” the pH level by adding several ounces of an acidic material(e.g., sodium bisulfate for spas and muriatic acid for swimming pools).The user must then test again after several hours to ensure that theproper amount of acidic material has been added. If the pH level isstill too high, the user must add additional acidic material and waitseveral hours once again. If the pH level is too low (sometimes theresult of today's busy, impatient consumer adding too much acidicmaterial), the user must add a pH-increasing chemical to the water. Thisrepeated addition of chemicals to the water of the water feature in anattempt to control the pH level and the sanitizing agent level issometimes referred to as “chemical warfare.” Some frustrated consumersoften end up draining their spas and starting over with fresh waterrather than spending the time and effort to “balance the water.” Otherfrustrated consumers simply ignore the pH level of the water altogether,which can result in unsanitary conditions due to the reduced efficacy ofthe sanitizing agent.

Some systems for control of pH levels and/or sanitizing agent levelsutilize a peristaltic or diaphragm pump and an open tank. The pumpforces a solution into the plumbing of the water feature, usuallydownstream of the water heater. Peristaltic pumps often require frequenttubing replacements (e.g., every three to six months, depending onusage). Other systems utilize cartridges which are connected viaflexible tubing to both the suction and pressure plumbing of the watercirculation system. Such systems have the disadvantage of feedingconcentrated chlorine at a low pH level directly into the circulationsystem ahead of the heater, pump, and filter, potentially causingcorrosion of these components. Such older systems have largely beenreplaced by inline feeders which introduce sanitizing agent directlyinto the plumbing through a pressure differential. These systems can beplaced after the heater and other circulation system components.

Other systems for control of sanitizing agent levels utilize a venturifeed and an open tank. The venturi feed creates a vacuum which drawssolution into a tee where the solution is mixed with the water beingcirculated. The feed can be controlled through the use of valves or bymanually adjusting a valve on the vacuum side of the tee. Such systemsare prone to clogging of the injector orifices.

Erosion feeders are most commonly used on residential and smallcommercial pools for control of sanitizing agent levels. For example, afeeder containing chlorine tablets can be installed in the return-lineplumbing. The tablets are exposed to the flowing stream, and graduallydissolve. Such systems are typically manually adjusted.

Liquid feeders are most commonly used on residential pools. In certainsuch system, an open tank feeder containing liquid chlorine is connectedto the suction and pressure sides of the circulation system. Air isallowed into the feeder to replace the solution as the contents aredepleted. A float valve in the feeder maintains the water level in thefeeder. Such systems can not be installed below the water level of thewater feature due to backflow. Concentrated chlorine enters the waterpump and water heater in this arrangement and can damage variousequipment of the water feature. Additionally, failure of the floatsystem can cause loss of pool water.

Automatic control of the pH level of a water feature is furthercomplicated by periodic recalibration of the pH controller. Typical pHelectrodes have a reference potential defined by a reference gel orsolution. This reference material is depleted through migration throughthe porous junction, resulting in changes of the reference potential.Typically, to calibrate an automatic pH control system, a user mustprepare a standard buffer solution (e.g., a pH 7.0 buffer) as astandardizing calibrant, and put the pH controller in calibration mode.The user removes the pH sensor, places it in the container of buffersolution, and recalibrates the pH controller. This procedure can bequite difficult for a user. In addition, the location of the pH sensorcan make it difficult to access. The recalibration process is typicallyperformed monthly, or even weekly in some cases, and can require moreeffort than simply testing and adding chemicals.

SUMMARY OF THE INVENTION

In certain embodiments, a system automatically maintains at least one ofa pH level and a sanitizing agent level of water in a water feature. Thesystem is fluidly coupled to the water feature. The system comprises asensor assembly fluidly coupled to the water feature. The sensorassembly is responsive to at least one of a pH level of the water and asanitizing agent level of the water. The sensor assembly is responsiveto the pH level by generating a pH signal corresponding to the pH level.The sensor assembly is responsive to the sanitizing agent level of thewater by generating a sanitization signal corresponding to thesanitizing agent level. The system further comprises a controlleroperatively coupled to the sensor assembly. The controller generatescontrol signals in response to at least one of the pH signal and thesanitization signal. The system further comprises at least one of afirst source and a second source. The first source comprises a firstvalve assembly and a first container containing an sanitizing agentmaterial. The first valve assembly is responsive to at least a portionof the control signals from the controller by selectively allowing thesanitizing agent material to flow from the first container to the waterfeature. The second source comprises a second valve assembly and asecond container containing a pH-modifying material. The second valveassembly is responsive to at least a portion of the control signals fromthe controller by selectively allowing the pH-modifying material to flowfrom the second container to the water feature. The system furthercomprises a third source comprising a third valve assembly and a thirdcontainer containing a liquid calibrant material. The third valveassembly is responsive to at least a portion of the control signals fromthe controller by selectively allowing the calibrant material to flowfrom the third container through the sensor assembly to the waterfeature.

In certain embodiments, a sanitization system automatically controls thepH level and sanitizing agent level of a water feature. The sanitizationsystem comprises a water circulation system in fluid communication withthe water feature. The sanitization system further comprises asanitizing agent source in fluid communication with the watercirculation system. The sanitizing agent source comprises a sanitizingagent material. The sanitization system further comprises a pH-modifyingmaterial source in fluid communication with the water circulationsystem. The pH-modifying material source comprises a pH-modifyingmaterial. The sanitization system further comprises a sanitizing agentsensor including a probe in fluid contact with water in the watercirculation system. The sanitizing agent sensor generates a sanitizingagent output signal indicative of a sanitizing agent level in the water.The sanitization system further comprises a pH sensor including a probein fluid contact with the water in the water circulation system. The pHsensor generates a pH output signal indicative of a pH level in thewater. The sanitization system further comprises a calibrant materialsource in fluid communication with at least one of the sanitizing agentsensor and the pH sensor. The calibrant material source comprises acalibrant material having at least one of a predetermined pH level and apredetermined sanitizing agent level. The sanitization system furthercomprises a control system responsive to the sanitizing agent outputsignal by selectively switching the sanitizing agent source between anactive state in which the sanitizing agent source adds sanitizing agentmaterial to the water and an inactive state in which the sanitizingagent source does not add sanitizing agent material to the water so asto maintain the sanitizing agent level within a first preset range. Thecontrol system is further responsive to the pH output signal byselectively switching the pH-modifying material source between an activestate in which the pH-modifying material source adds pH-modifyingmaterial to the water and an inactive state in which the pH-modifyingmaterial source does not add pH-modifying material to the water so as tomaintain the pH level within a second preset range. The control systemis further configured to recalibrate at least one of the sanitizingagent output signal and the pH output signal by selectively switchingthe calibrant material source between an active state in which thecalibrant material source introduces calibrant material to at least oneof the sanitizing agent sensor and the pH sensor and an inactive statein which the calibrant material source does not introduce calibrantmaterial to at least one of the sanitizing agent sensor and the pHsensor.

In certain embodiments, a system measures a chemical level of water in awater feature. The system is fluidly coupled to the water feature. Thesystem comprises a sensor assembly fluidly coupled to the water feature.The sensor assembly is responsive to the chemical level of the water bygenerating a signal corresponding to the chemical level. The systemfurther comprises a controller operatively coupled to the sensorassembly. The controller uses a calibration function to calculate thechemical level in response to the signal generated by the sensorassembly. The controller generates a calibrant control signal. Thesystem further comprises a calibrant source comprising a calibrantmaterial. The calibrant source is responsive to the calibrant controlsignal from the controller by selectively allowing the calibrantmaterial to flow from the calibrant source to the sensor assembly. Thecontroller calculates the calibration function while the calibrantmaterial flows from the calibrant source to the sensor assembly.

In certain embodiments, a source controllably adds a chemical materialto a water circulation system of a water feature. The source comprises acontainer which comprises an inlet and an outlet. The container furthercomprises a vessel having a lower portion and an upper portion. Thelower portion contains the chemical material and is removably coupledand fluidly coupled to the inlet. The upper portion of the vessel isremovably coupled and fluidly coupled to the outlet. The source furthercomprises a first valve fluidly coupled to the water circulation systemand to the inlet. The first valve is selectively opened to fluidlycouple the water circulation system and the inlet. The source furthercomprises a second valve fluidly coupled to the water circulation systemand to the outlet. The second valve is selectively opened to fluidlycouple the water circulation system and the outlet. Upon opening thefirst valve and the second valve, water flows from the water circulationsystem through the inlet, into the lower portion of the vessel, mixeswith the chemical material, flows out of the upper portion of thevessel, through the outlet to the water circulation system.

In certain embodiments, a source controllably adds a liquid chemicalmaterial to a water circulation system of a water feature. At least aportion of the circulation system comprises water having a firstpressure. The source comprises a container comprising an inlet and anoutlet. The container further comprises a vessel containing the liquidchemical material. The vessel is removably coupled and fluidly coupledto the inlet and to the outlet. The source further comprises a firstvalve fluidly coupled to a fluid at a second pressure and to the inlet.The first valve is selectively opened to expose the inlet to the secondpressure. The second pressure is larger than the first pressure. Thesource further comprises a second valve fluidly coupled to the outletand to the portion of the circulation system comprising water having thefirst pressure. The second valve is selectively opened to fluidly couplethe outlet and the portion of the circulation system comprising waterhaving the first pressure. Upon opening the first valve and the secondvalve, the liquid chemical material flows from the vessel through theoutlet to the portion of the circulation system comprising water havingthe first pressure.

In certain embodiments, a sensor assembly senses a chemical level inwater of a water feature. The sensor assembly comprises a pH sensor. Thesensor assembly further comprises a sanitizing agent sensor. The pHsensor and the sanitizing agent sensor share a common referenceelectrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 schematically illustrate various exemplary systems forautomatically maintaining at least one of a pH level and a sanitizingagent level of water in the water feature.

FIGS. 5A and 5B schematically illustrate two exemplary configurations ofa first source compatible with embodiments described herein.

FIGS. 6A and 6B schematically illustrate two states of an exemplaryfirst valve assembly comprising a pinch valve compatible withembodiments described herein.

FIGS. 7A and 7B schematically illustrate two exemplary configurations ofa second source comprising a second valve assembly and a secondcontainer.

FIGS. 8A and 8B schematically illustrate two exemplary configurations ofa third source comprising a third valve assembly and a third container.

FIG. 9 is a perspective exploded view of an exemplary containercompatible for use as a first container or as a second container inaccordance with embodiments described herein.

FIG. 10 is a perspective view of an exemplary cartridge compatible withembodiments described herein.

FIG. 11 is a perspective view of an exemplary insert compatible withembodiments described herein.

FIG. 12 is a perspective view of an exemplary insert cover compatiblewith embodiments described herein.

FIGS. 13A and 13B are two perspective views of an exemplary cartridge,top compatible with embodiments described herein.

FIG. 14 schematically illustrates in perspective view an exemplary firsthousing portion compatible with embodiments described herein.

FIG. 15A is a perspective view of an exemplary second housing portioncompatible with embodiments described herein.

FIG. 15B is a perspective view of an exemplary end portion compatiblewith embodiments described herein.

FIG. 16 schematically illustrates an exemplary container compatible withembodiments in which the chemical material within the container is inliquid form.

FIG. 17 schematically illustrates an exemplary sensor assemblycompatible with embodiments described herein.

FIG. 18A schematically illustrates an exemplary microprocessor and otherexemplary control circuitry for the system.

FIG. 18B schematically illustrates an exemplary circuit of a powersupply for the system.

FIG. 18C schematically illustrates an exemplary circuit used forsolenoid control for the first valve assembly, the second valveassembly, and the third valve assembly.

FIG. 18D schematically illustrates an exemplary circuit used during pHlevel measurements.

FIG. 18E schematically illustrates an exemplary circuit used duringsterilizing agent level measurements.

FIG. 18F schematically illustrates an exemplary circuit used duringtotal-dissolved-solid level measurements.

FIG. 19 schematically illustrates an exemplary system compatible withembodiments described herein.

FIG. 20A is a flow diagram of an exemplary measurement cycle compatiblewith embodiments described herein.

FIG. 20B schematically illustrates an exemplary fluid flow pattern forthe system when in the measurement mode.

FIG. 21 is a flow diagram of an exemplary process for measuring thetotal-dissolved-solid (TDS) level using the amperometric sensor.

FIG. 22 is a flow diagram of an exemplary process for measuring the pHlevel.

FIG. 23 is a flow diagram of an exemplary process for measuring thesanitizing agent level.

FIG. 24 is a flowchart of an exemplary process in which the reading fromthe amperometric sensor is converted into parts-per-million (ppm).

FIG. 25 is a graph of the HOCl⁻ percentage and the OCl⁻ percentage as afunction of pH.

FIG. 26 is a flowchart of an exemplary process in which the systemchecks the delta of the chlorine level measurements.

FIG. 27A is a flow diagram of an exemplary process for adding thepH-modifying material to the water feature.

FIG. 27B schematically illustrates the fluid flow pattern of the systemcorresponding to FIG. 27A.

FIG. 28 schematically illustrates the fluid flow pattern for the systemwhen adding sterilizing agent material to the water feature.

FIG. 29 schematically illustrates a fluid flow pattern for the systemduring the auto-calibration cycle.

FIG. 30 is a flow diagram of an exemplary auto-calibration cyclecompatible with embodiments described herein.

FIG. 31 schematically illustrates another configuration of the systemwhich allows partial mixing compatible with certain embodimentsdescribed herein.

FIG. 32 schematically illustrates another configuration of the systemwhich utilizes liquid sanitizing agent material and liquid pH-modifyingmaterial.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

System Overview

FIG. 1 schematically illustrates an exemplary system 100 fluidly coupledto a water feature (e.g., spa, Jacuzzi, jetted tub, whirlpool bath, orswimming pool) for automatically maintaining at least one of a pH leveland a sanitizing agent level of water in the water feature. As usedherein, the term “fluidly coupled” describes configurations having afluid pathway for direct fluid flow from a first component to a secondcomponent, and configurations having a fluid pathway for indirect fluidflow from one component to another (e.g., fluid flow through one or moreadditional components to flow from the first component to the secondcomponent).

The system 100 comprises a sensor assembly 110 fluidly coupled to thewater feature. The sensor assembly 110 is responsive to at least one ofa pH level of the water and a sanitizing agent level of the water. Thesensor assembly 110 is responsive to the pH level by generating a pHsignal corresponding to the pH level. The sensor assembly 110 isresponsive to the sanitizing agent level of the water by generating asanitization signal corresponding to the sanitizing agent level. Thesystem 100 further comprises a controller 120 operatively coupled to thesensor assembly 110. The controller 120 generates control signals inresponse to at least one of the pH signal and the sanitization signal.The system 100 further comprises at least one of a first source 130 anda second source 140. The first source 130 comprises a first valveassembly 132 and a first container 134 containing a sanitizing agent.The first valve assembly 132 is responsive to at least a portion of thecontrol signals from the controller 120 by selectively allowing thesanitizing agent to flow from the first container 134 to the waterfeature. The second source 140 comprises a second valve assembly 142 anda second container 144 containing a pH-modifying material. The secondvalve assembly 142 is responsive to at least a portion of the controlsignals from the controller 120 by selectively allowing the pH-modifyingmaterial to flow from the second container 144 to the water feature. Thesystem 100 further comprises a third source 150 comprising a third valveassembly 152 and a third container 154 containing a liquid calibrantmaterial. The third valve assembly 152 is responsive to at least aportion of the control signals from the controller 120 by selectivelyallowing the calibrant material to flow from the third container 154through the sensor assembly 110 to the water feature.

FIG. 2 schematically illustrates another exemplary system 200 fluidlycoupled to a water feature for automatically maintaining at least one ofa pH level and a sanitizing agent level of water in the water feature.The system 200 comprises the sensor assembly 110, controller (not shownin FIG. 2 for clarity), first source 130, first valve assembly 132,first container 134, second source 140, second valve assembly 142,second container 144, third source 150, third valve assembly 152, andthird container 154 as schematically illustrated in FIG. 1.

The system 200 schematically illustrated by FIG. 2 further comprises apressure manifold 210 fluidly coupled to the water feature, the firstvalve assembly 130, and the second valve assembly 140. The system 200further comprises a vacuum manifold 220 fluidly coupled to the firstvalve assembly 130, the second valve assembly 140, the third valveassembly 150, and the sensor assembly 110. The vacuum manifold 220 isfluidly coupled to the water feature through the sensor assembly 110.The pressure manifold 210 provides ports for connecting tubing from thecirculation system of the water feature to the first source 130, thesecond source 140, and the third source 150. The vacuum manifold 220provides ports for connecting tubing from the first source 130, thesecond source 140, and the third source 150 to the sensor assembly 110,thereby allowing sterilizing agent and/or pH-modifying material, orcalibrant material to flow through the sensor assembly 110. In certainembodiments, the pressure manifold 210 provides the motive force throughthe first container 134 and the second container 144 and augments thelower pressure from the vacuum manifold 220. In certain embodiments, thelower pressure of the vacuum manifold 220 is below atmospheric pressure.

FIG. 3 schematically illustrates another exemplary system 300 fluidlycoupled to a water feature for automatically maintaining at least one ofa pH level and a sanitizing agent level of water in the water feature.The system 300 comprises the sensor assembly 110, controller (not shownin FIG. 3 for clarity), first source 130, first valve assembly 132,first container 134, second source 140, second valve assembly 142,second container 144, third source 150, third valve assembly 152, andthird container 154 as schematically illustrated in FIG. 1. The system300 further comprises the pressure manifold 210 and the vacuum manifold220 as schematically illustrated in FIG. 2. In the system 300schematically illustrated by FIG. 3, the first valve assembly 132 isfluidly coupled to the second valve assembly 142. Furthermore, thesecond valve assembly 140 is fluidly coupled to the third valve assembly150. Each of the first valve assembly 132, the second valve assembly142, and the third valve assembly 152 is responsive to at least aportion of the control signals from the controller (not shown) byallowing water to flow from the pressure manifold 210, through the firstvalve assembly 132, through the second valve assembly 142, through thethird valve assembly 152, to the vacuum manifold 220.

The system 300 schematically illustrated by FIG. 3 further comprises aflow sensor 310 and a venturi tee 320. The flow sensor 310 is fluidlycoupled to a circulation pump line of the water feature and isresponsive to a flow rate through the circulation system by generating aflow signal indicative of the flow rate. The controller (not shown) isresponsive to the flow signal from the flow sensor 310. In certainembodiments, the flow sensor 310 comprises a flow switch fluidly coupledto the pressure manifold 210, as schematically illustrated by FIG. 3.The flow switch indicates whether the water flow through the system 300is above an adequate flow rate for operation of the system 300 (e.g.,approximately 10 gallons per hour). In other embodiments, the flowsensor 310 comprises a paddle wheel flow sensor. In certain otherembodiments, the flow sensor 310 comprises a differential pressureswitch fluidly coupled to the venturi tee 320. The differential pressureswitch responds to the pressure before and after the venturi tee 320,thereby measuring the pressure drop through the venturi tee 320 (e.g.,approximately 2 pounds per square inch) which indicates whether adequateflow is present for operation of the system 300.

The venturi tee 320 schematically illustrated by FIG. 3 is fluidlycoupled to a circulation pump line of the water feature such that waterof the water feature flows through the venturi tee 320. In certainembodiments, the venturi tee 320 is a component of the system 300, whilein other embodiments, the venturi tee 320 is a component of thecirculation system of the water feature. The vacuum manifold 220 isfluidly coupled to the circulation system of the water feature throughthe sensor assembly 110 and through the venturi tee 320. The venturi tee320 creates a pressure differential, the low-pressure side of which istied to the outlet of the sensor assembly 110. In certain embodiments,the low-pressure side of the venturi tee 320 is below atmosphericpressure.

In each of the exemplary systems 100, 200, 300, water from the waterfeature enters the first source 130. Under certain configurations of thefirst valve assembly 132, the water flows from the first valve assembly132 through the sensor assembly 110 back to the water feature. Undercertain other configurations of the first valve assembly 132, sanitizingagent from the first container 134 flows from the first valve assembly132 through the sensor assembly 110 to the water feature. As describedmore fully below, in certain embodiments, the first source 130selectively allows both water and sanitizing agent from the firstcontainer 134 to flow from the first valve assembly 132 through thesensor assembly 110 to the water feature.

In each of the exemplary systems 100, 200, 300, water from the waterfeature enters the second source 140. Under certain configurations ofthe second valve assembly 142, the water flows from the second valveassembly 142 through the sensor assembly 110 back to the water feature.Under certain other configurations of the second valve assembly 142,pH-modifying material from the second container 144 flows from thesecond valve assembly 142 through the sensor assembly 110 to the waterfeature. As described more fully below, in certain embodiments, thesecond source 140 selectively allows both water and pH-modifyingmaterial from the second container 144 to flow from the second valveassembly 142 through the sensor assembly 110 to the water feature.100641 Under certain configurations of the third source 150, the thirdvalve assembly 152 selectively allows calibrant material from the thirdcontainer 154 to flow from the third container 154 through the sensorassembly 110 to the water feature. In certain such embodiments, thefirst valve assembly 132 and/or the second valve assembly 142 areconfigured to interrupt flow of the water from the water feature throughthe sensor assembly 110 back to the water feature.

FIG. 4 schematically illustrates another exemplary system 400 fluidlycoupled to a water feature for automatically maintaining at least one ofa pH level and a sanitizing agent level of water in the water feature.The system 400 comprises the sensor assembly 110, controller (not shownin FIG. 4 for clarity), first source 130, first valve assembly 132,first container 134, second source 140, second valve assembly 142,second container 144, third source 150, third valve assembly 152, andthird container 154 as schematically illustrated in FIG. 1. The system400 further comprises the pressure manifold 210 and the vacuum manifold220 as schematically illustrated in FIG. 2. The system 400 furthercomprises the flow sensor 310 and the venturi tee 320 as schematicallyillustrated in FIG. 3. While the exemplary system 400 schematicallyillustrated by FIG. 4 is referred to below when describing varioussystem components, other configurations are also compatible withembodiments described herein.

Installation of the System

In certain embodiments, the system 400 is an integral portion of thecirculation system of the water feature (e.g., installed as part of anew water feature). In certain other embodiments, the system 400 isinstalled or retrofitted in the circulation system of an existing waterfeature. For example, the system 400 can be installed by tapping into acirculation line of an existing water feature and installing a venturiinjector and a pressure tee. Certain such embodiments use the pressureand vacuum created by the circulation system to motivate fluids from thefirst source 130, the second source 140, and the third source 150through the system 100 and obviates the use of a chemical pump. Wheninstalled on an existing water feature, the system 400 can be placed invarious positions (e.g., on the side or under the skirt of an existingspa).

In certain embodiments, the system 400 is installed to provide easyaccess by the user to the first container 134, the second container 144,the third container 154, and the sensor assembly 110 to facilitatereplacement by the user, as described more fully below. The system 400of certain embodiments is enclosed in a housing which is rain- andsplash-resistance. The housing can comprise a hinged cover which allowsaccess to the containers 134, 144, 154 and which improves the appearanceof the system 400.

In certain embodiments, the system 400 is installed in a spa having acirculation pump (e.g., a 24-hour circulation pump) and having awall-fitting ozone injector. The ozone injector of certain embodimentshas an integral venturi tee or a separate venturi tee. The pressurizedfluid stream from the circulation pump of certain embodiments throughthe ozone injector creates a vacuum on the venturi tee. The vacuum isused to feed liquid into the flowing stream. In certain embodiments, anadditional tee is placed before the venturi tee to create back pressureand to provide an additional outlet for the pressure water feed used toreplace fluid withdrawn through the vacuum line. In certain otherembodiments, the system 400 is installed in a spa with an inline venturiinjector rather than an ozone injector. In certain other embodiments,the system 400 is installed in a spa or a swimming pool having atwo-speed circulation pump, a tee, and an ozone jet or venturi tee.

In certain embodiments, a user may desire to use ozone for oxidation inaddition to the chemical feed system 400. In certain such embodiments,two venturi injectors are used in parallel, one for the ozone unit andone for the chemical feed system 400. In certain embodiments, an airtrap is added to the circulation line. For example, a large diameter teewith a small side outlet which is oriented downward can be used toprevent entrained bubbles from entering the sensor assembly 110.

Valve Assembly

FIG. 5A schematically illustrates a first source 130 compatible withembodiments described herein. As schematically illustrated by FIG. 5A,the first valve assembly 132 comprises a first inlet 510, a second inlet512, a third inlet 514, a first outlet 516, a second outlet 518, and athird outlet 520. The first inlet 510 and the first outlet 516 arefluidly coupled together by a first valve 522. The second inlet 512 andthe second outlet 518 are fluidly coupled together by a second valve524. The third inlet 514 and the third outlet 520 are fluidly coupledtogether by a third valve 526.

In certain embodiments in which the first container 134 comprises a drychemical sterilizing agent, the first inlet 510 and the second inlet 512each receives water flowing from the pressure manifold 210. Waterreceived by the first inlet 510 is selectively allowed to flow throughthe first valve 522 to the first outlet 516 and into the first container134 where the water mixes with the sterilizing agent. Water andsterilizing agent flowing from the first container 134 is received bythe third inlet 514 and is selectively allowed to flow through the thirdvalve 526 to the third outlet 520. Water and sterilizing agent exitingthrough the third outlet 520 flows to the vacuum manifold 220. Waterreceived by the second inlet 512 is selectively allowed to flow throughthe second valve 524 to the second outlet 518. Water exiting through thesecond outlet 518 flows to the second valve assembly 142.

In certain embodiments in which the first container 134 comprises aliquid chemical sterilizing agent, the first inlet 510 receives a liquid(e.g., air or other gas) at approximately atmospheric pressure and thesecond inlet 512 receives water flowing from the pressure manifold 210.Air received by the first inlet 510 is selectively allowed to flowthrough the first valve 522 to the first outlet 516 and into the firstcontainer 134. Liquid sterilizing agent flowing from the first container134 is received by the third inlet 514 and is selectively allowed toflow through the third valve 526 to the third outlet 520. Sterilizingagent exiting through the third outlet 520 flows to the vacuum manifold220. Water received by the second inlet 512 is selectively allowed toflow through the second valve 524 to the second outlet 518. Waterexiting through the second outlet 518 flows to the second valve assembly142.

In certain embodiments in which the first container 134 comprises aliquid chemical sterilizing agent, the first container 134 receives airor other gas from the first valve 522 to provide pressure which allowsliquid sterilizing agent to flow from the first container 134 into thethird inlet 514 of the first valve assembly 132. In certain otherembodiments, the first container 134 receives air or other gas from avent 528 which is not directly connected to the first valve assembly132. In such embodiments, the first valve assembly 132 comprises twoinlets 512, 514, two outlets 518, 520, and two valves 524, 526, asschematically illustrated by FIG. 5B. Certain such embodimentsadvantageously allow liquid sterilizing agent to be withdrawn from thefirst container 134 without dilution of the liquid remaining in thefirst container 134 by water from the water feature.

Returning to the configuration schematically illustrated by FIG. 5A inwhich the first container 134 comprises a dry chemical sterilizingagent, in a first state of the first valve assembly 132, water isallowed to flow from the pressure manifold 210 into the first container134 and out to the vacuum manifold 220. In this first state, the firstvalve 522 is open, the second valve 524 is closed, and the third valve526 is open. In a second state of the first valve assembly 132, water isallowed to flow from the pressure manifold 210 to the second valveassembly 142. In this second state, the first valve 522 is closed, thesecond valve 524 is open, and the third valve 526 is closed. In certainembodiments, the first valve assembly 132 is responsive to at least aportion of the control signals from the controller (not shown) byswitching between the first state and the second state. By selectivelyactuating the valves 522, 524, 526 of the first valve assembly 132,certain embodiments advantageously allow a portion of the sterilizingagent in the first container 134 to flow through the sensor assembly 110into the water feature.

In certain embodiments, the first valve 522 and the third valve 526 areclosed when not being energized, and the second valve 524 is open whennot being energized. Such embodiments advantageously avoid unwanted flowof sterilizing agent into the water feature in the event of a powerfailure. In certain embodiments, the valves 522, 524, 526 are actuatedsubstantially simultaneously by the controller, while in otherembodiments, one or more of the valves 522, 524, 526 are individuallyactuated to allow or to inhibit flow through the individual valve.

FIGS. 6A and 6B schematically illustrate two states of an exemplaryfirst valve assembly 132 comprising a pinch valve 530 compatible withembodiments described herein. The pinch valve 530 comprises a movableplunger 532, a pair of stationary walls 534, and sections of flexibletubing 536 positioned between the plunger 532 and one of the stationarywalls 534. These sections of flexible tubing 536 correspond to the firstvalve 522, the second valve 524, and the third valve 526. When the pinchvalve 530 is energized, as schematically illustrated by FIG. 6A, theplunger 532 is in a first position in which the tubing 536 correspondingto the first valve 522 and the third valve 526 is open and the tubing536 corresponding to the second valve 524 is squeezed closed between theplunger 532 and one of the stationary walls 534. When the pinch valve530 is not energized, as schematically illustrated by FIG. 6B, theplunger 532 is in a second position in which the tubing 536corresponding to the first valve 522 and the third valve 526 is squeezedclosed between the plunger 532 and one of the stationary walls 534, andthe tubing 536 corresponding to the second valve 524 is open.

Various actuation mechanisms for the pinch valve 530 are compatible withembodiments described herein. An exemplary set of solenoid-actuatedpinch valves 530, corresponding to the first valve assembly 132, thesecond valve assembly 142, and the third valve assembly 152 isschematically illustrated by FIG. 6C. Each solenoid-actuated pinch valve530 comprises an electromagnet 540 and springs (not shown) which arecoupled to the plunger 532 (not shown in FIG. 6C). Focusing on the firstvalve assembly 132, when the pinch valve 530 is energized, theelectromagnet 540 moves the plunger 532 against the force of the springsinto the first position in which the tubings 536 of the first valve 522and the third valve 526 are open and the tubing 536 of the second valve524 is pinched closed. When the pinch valve 530 is not energized, thesprings force the plunger 532 into the second position in which thetubings 536 of the first valve 522 and the third valve 526 are pinchedclosed and the tubing 536 of the second valve 524 is open. Actuation ofthe electromagnet 540 therefore moves the plunger 532 between the firstposition of FIG. 6A and the second position of FIG. 6B to actuate thepinch valve 530. Exemplary electromagnets 540 compatible withembodiments described herein include, but are not limited to, a tubularE-09-150 electromagnet available from Magnetic Sensor Systems of VanNuys, Calif.

Tubing 536 compatible with embodiments described herein includes, but isnot limited to, C-Flex® tubing available from Cole-Parmer InstrumentCompany of Vernon Hills, Illinois, and Norprene® tubing available fromSaint-Gobain Performance Plastics of Akron, Ohio. Various dimensions oftubing may be used. For example, tubing with an inner diameter of ⅛″ andan outer diameter of ¼″ advantageously minimizes clogging of tubes andorifices. The tubing 536 preferably does not have a high compression setand has a low hardness so as to conserve power and to allow the use ofsmaller solenoids or electromagnets.

In certain embodiments, heat generated by the solenoid or electromagnet540 is transferred to the water and from the water to a housingcomprising the system 400. A heat sink is used in certain embodiments totransfer the heat from the electromagnet 540 to the water. The heat sinkof certain embodiments comprises stainless-steel tubing thermallycoupled to the electromagnet 540 and through which water from the waterfeature flows. In certain such embodiments in which the water feature isused outdoors, the heat sink advantageously warms the housing to preventtubing within the housing from freezing.

In certain embodiments, use of one or more pinch valves in at least oneof the valve assemblies 132, 142, 152 advantageously prevents corrosionor clogging of valves or components since the pinch valve mechanism hasno direct contact with the corrosive fluids which are used as thesanitizing agent or the pH-modifying material. In certain otherembodiments in which the pinch valves are closed when not energized, useof one or more pinch valves in at least one of the valve assemblies 132,142, 152 advantageously provides “fail-safe” operation in which thecontents of the corresponding containers 134, 144, 154 are preventedfrom entering the water feature upon a power failure.

In certain other embodiments, use of one or more pinch valves in atleast one of the valve assemblies 132, 142, 152 advantageously protectsthe system from pressure buildup. For example, spa use can be infrequentsuch that chemical feed is not needed for a period of days or weeks.During these extended periods of inactivity, the sealed containers arepressurized and can develop very high pressures, particularly if thetemperature rises significantly. Pinch valves typically have a pressurelimit beyond which the pinch valve does not completely close (e.g.,approximately 20 pounds per square inch), so they have an inherentpressure relief mechanism. For example, if the pressure in a containerexceeds the pressure limit of the corresponding pinch valve, the pinchvalve “leaks” and the excess pressure is vented through the pinch valveso as to equalize the pressure within the container to below thepressure limit.

FIG. 7A schematically illustrates an exemplary second source 140comprising a second valve assembly 142 and a second container 144comprising a dry chemical pH-modifying material. Similar to the firstvalve assembly 132 of FIG. 5A, the second valve assembly 142 of FIG. 7Acomprises a first inlet 610, a second inlet 612, a third inlet 614, afirst outlet 616, a second outlet 618, and a third outlet 620. The firstinlet 610 and the first outlet 616 are fluidly coupled together by afirst valve 622. The second inlet 612 and the second outlet 618 arefluidly coupled together by a second valve 624. The third inlet 614 andthe third outlet 620 are fluidly coupled together by a third valve 626.

In certain embodiments in which the second container 144 comprises a drypH-modifying material, the first inlet 610 receives water flowing fromthe pressure manifold 210. The second inlet 612 receives water flowingfrom the first valve assembly 132 (e.g., from the second outlet 518 ofthe first valve assembly 132). Water received by the first inlet 610 isselectively allowed to flow through the first valve 622 to the firstoutlet 616 and into the second container 144 where the water mixes withthe dry chemical pH-modifying material. Water and the pH-modifyingmaterial flowing from the second container 144 is received by the thirdinlet 614 and is selectively allowed to flow through the third valve 626to the third outlet 620. Water and the pH-modifying material exitingthrough the third outlet 620 flows to the vacuum manifold 220. Waterreceived by the second inlet 612 is selectively allowed to flow throughthe second valve 624 to the second outlet 618. Water exiting through thesecond outlet 618 flows to the third valve assembly 152.

In certain embodiments in which the second container 144 comprises aliquid chemical pH-modifying material, the first inlet 610 receives aliquid (e.g., air or other gas) at approximately atmospheric pressureand the second inlet 612 receives water flowing from the pressuremanifold 210. Air received by the first inlet 610 is selectively allowedto flow through the first valve 622 to the first outlet 616 and into thesecond container 144. Liquid pH-modifying material flowing from thesecond container 144 is received by the third inlet 614 and isselectively allowed to flow through the third valve 626 to the thirdoutlet 620. The pH-modifying material exiting through the third outlet620 flows to the vacuum manifold 220. Water received by the second inlet612 is selectively allowed to flow through the second valve 624 to thesecond outlet 618. Water exiting through the second outlet 618 flows tothe third valve assembly 152.

In certain embodiments, the first valve 622 and the third valve 626 areclosed when not being energized, and the second valve 624 is open whennot being energized. Such embodiments advantageously avoid unwanted flowof the pH-modifying material into the water feature in the event of apower failure. In certain embodiments, the valves 622, 624, 626 areactuated simultaneously by the controller, while in other embodiments,one or more of the valves 622, 624, 626 are individually actuated toallow or to inhibit flow through the individual valve. In certainembodiments, one or more of the valves 622, 624, 626 comprise a pinchvalve, as described more fully above in relation to FIGS. 6A-6C.

In certain embodiments in which the second container 144 comprises aliquid chemical pH-modifying material, the second container 144 receivesair or other gas from the first valve 622 to provide pressure whichallows liquid pH-modifying material to flow from the second container144 into the third inlet 614 of the second valve assembly 142. Incertain other embodiments, the second container 144 receives air orother gas from a vent 628 which is not directly connected to the secondvalve assembly 142. In such embodiments, the second valve assembly 142comprises two inlets 612, 614, two outlets 618, 620, and two valves 624,626, as schematically illustrated by FIG. 7B. Certain such embodimentsadvantageously allow liquid pH-modifying material to be withdrawn fromthe second container 144 without dilution of the liquid remaining in thesecond container 144 by water from the water feature.

Returning to the configuration schematically illustrated by FIG. 7A inwhich the second container 144 comprises a dry chemical pH-modifyingmaterial, in a first state of the second valve assembly 142, water isallowed to flow from the pressure manifold 210 into the second container144 and out to the vacuum manifold 220. In this first state, the firstvalve 622 is open, the second valve 624 is closed, and the third valve626 is open. In a second state of the second valve assembly 142, wateris allowed to flow from the first valve assembly 132 to the third valveassembly 152. In this second state, the first valve 622 is closed, thesecond valve 624 is open, and the third valve 626 is closed. In certainembodiments, the second valve assembly 142 is responsive to at least aportion of the control signals from the controller (not shown) byswitching between the first state and the second state. By selectivelyactuating the valves 622, 624, 626 of the second valve assembly 142,certain embodiments advantageously allow a portion of the pH-modifyingmaterial in the second container 144 to flow through the sensor assembly110 into the water feature.

FIG. 8A schematically illustrates a third source 150 comprising a thirdvalve assembly 152 and a third container 154 comprising a liquidcalibrant material. Similar to the first valve assembly 132 of FIG. 5A,the third valve assembly 152 of FIG. 8A comprises a first inlet 710, asecond inlet 712, a third inlet 714, a first outlet 716, a second outlet718, and a third outlet 720. The first inlet 710 and the first outlet716 are fluidly coupled together by a first valve 722. The second inlet712 and the second outlet 718 are fluidly coupled together by a secondvalve 724. The third inlet 714 and the third outlet 720 are fluidlycoupled together by a third valve 726.

In certain embodiments, the first inlet 710 receives a liquid (e.g., airor other gas) at approximately atmospheric pressure and the second inlet712 receives water flowing from the second outlet 618 of the secondvalve assembly 142. Air received by the first inlet 710 is selectivelyallowed to flow through the first valve 722 to the first outlet 716 andinto the third container 154. Liquid calibrant material flowing from thethird container 154 is received by the third inlet 714 and isselectively allowed to flow through the third valve 726 to the thirdoutlet 720. Calibrant material exiting through the third outlet 720flows to the vacuum manifold 220. Water received by the second inlet 712is selectively allowed to flow through the second valve 724 to thesecond outlet 718. Water exiting through the second outlet 718 flows tothe vacuum manifold 220.

In certain embodiments, the first valve 722 and the third valve 726 areclosed when not being energized, and the second valve 724 is open whennot being energized. Such embodiments advantageously avoid unwanted flowof the calibrant material into the water feature in the event of a powerfailure. In certain embodiments, the valves 722, 724, 726 are actuatedsimultaneously by the controller, while in other embodiments, one ormore of the valves 722, 724, 726 are individually actuated to allow orto inhibit flow through the individual valve. In certain embodiments,one or more of the valves 722, 724, 726 comprise a pinch valve, asdescribed more fully above in relation to FIGS. 6A-6C.

In certain embodiments, the third container 154 receives air or othergas from the first valve 722 to provide pressure which allows thecalibrant material to flow from the third container 154 into the thirdinlet 714 of the third valve assembly 152. In certain other embodiments,the third container 154 receives air or other gas from a vent 728 whichis not directly connected to the third valve assembly 152. In suchembodiments, the third valve assembly 152 comprises two inlets 712, 714,two outlets 718, 720, and two valves 724, 726, as schematicallyillustrated by FIG. 8B. Certain such embodiments advantageously allowliquid calibrant material to be withdrawn from the third container 154without dilution of the liquid remaining in the third container 154 bywater from the water feature.

Returning to the configuration schematically illustrated by FIG. 8A, ina first state of the third valve assembly 152, air is allowed to flowinto the third container 154 and calibrant material is allowed to flowout of the third container 154 to the vacuum manifold 220. Furthermore,in this first state, water is not allowed to flow from the second valveassembly 142 to the vacuum manifold 220. In this first state, the firstvalve 722 is open, the second valve 724 is closed, and the third valve726 is open. In a second state of the third valve assembly 152, water isallowed to flow from the second valve assembly 142 to the vacuummanifold 220 and calibrant material is not allowed to flow from thethird container 154 to the vacuum manifold 220. In this second state,the first valve 722 is closed, the second valve 724 is open, and thethird valve 726 is closed. In certain embodiments, the third valveassembly 152 is responsive to at least a portion of the control signalsfrom the controller (not shown) by switching between the first state andthe second state. By selectively actuating the valves 722, 724, 726 ofthe third valve assembly 152, certain embodiments advantageously allow aportion of the calibrant material in the third container 154 to flowthrough the sensor assembly 110 into the water feature.

Container

FIG. 9 is a perspective exploded view of an exemplary container 800which is compatible for use as a first container 134 or as a secondcontainer 144 in accordance with embodiments described herein. Thecontainer 800 comprises a cartridge 810, an insert 820, a gasket 830, aninsert cover 840, a cartridge top 850, a first housing portion 860, aplurality of O-rings 870 (e.g., three O-rings 870), a second housingportion 880, and an end portion 890. As described more fully below, whenassembled, the first housing portion 860, the second housing portion880, and the end portion 890 form a housing 900. In addition, whenassembled, the cartridge 810, the insert 820, the gasket 830, the insertcover 840, and the cartridge top 850 form a cartridge assembly 910.While the discussion below addresses particular configurations of thecontainer 800, other configurations are also compatible with embodimentsdescribed herein.

The cartridge 810 contains a chemical material to be introduced into thewater feature (e.g., sterilizing agent material or pH-modifyingmaterial). An exemplary cartridge 810 of the first container 134 holdsapproximately 1.5 pounds of dry sterilizing agent material. An exemplarycartridge 810 of the second container 144 holds approximately 2 poundsof dry pH-modifying material. Other sizes of cartridges 810 arecompatible with embodiments described herein.

In certain embodiments, the cartridge 810 is replaceable such that whenthe chemical material in the cartridge 810 is depleted, the cartridge810 can be removed and a new cartridge 810 installed in its place. Inother embodiments, the cartridge 810 is refillable such that when thechemical material in the cartridge 810 is depleted, the cartridge 810can be removed, additional chemical material is placed in the cartridge810, and the cartridge 810 is replaced. In certain embodiments, thecartridges 810 of the first container 134 and the second container 144have unique shapes or sizes to avoid the possibility of inadvertentswitching of sterilizing agent material with pH-modifying material, orvice versa. Other methods of avoiding inadvertent switching arecompatible with embodiments described herein.

In certain embodiments, as schematically illustrated in perspective viewby FIG. 10, the cartridge 810 comprises a vessel 811 (e.g., a bottle)with a generally cylindrical shape with an upper portion 812 and a lowerportion 813. The upper portion 812 comprises an edge surface 814 whichis configured to be coupled to the gasket 830. The upper portion 812further comprises a screw thread 815 which is reversibly connected to acap (not shown) during transportation and storage of the vessel 811. Incertain embodiments, the cap is child-proof to prevent the vessel 811from accidental opening and leakage of the chemical material duringtransportation and storage. The screw thread 815 is also reversiblyconnected to the cartridge top 850 during use. The upper portion 812 ofthe vessel 811 further comprises an inner surface 816 which isconfigured to support the insert 820 when placed in the container 810.In certain embodiments, the vessel 811 can hold approximately one poundof dry chemical material, while in other embodiments, other amounts ofthe chemical material can be accommodated within the vessel 811. Othershapes and configurations of the vessel 811 are also compatible withembodiments described herein.

As schematically illustrated in perspective view by FIG. 11, in certainembodiments, the insert 820 comprises a tubular conduit 821 having anupper portion 822 and a lower portion 823. The insert 820 furthercomprises a generally circular plate 824 with a plurality of holes 825,an inner annular ring 826 around the upper portion 822 of the tubularconduit 821, and an outer annular ring 827. When installed in the vessel811, the plate 824 and the outer annular ring 827 fit in the upperportion 812 of the vessel 811 with the lower portion 823 of the tubularconduit 821 extending into the lower portion 813 of the vessel 811. Theplate 824 fits onto the inner surface 816 of the vessel 811. In certainembodiments, the plate 824 is directly in contact with the inner surface816, while in other embodiments, a gasket is positioned between theplate 824 and the inner surface 816.

The tubular conduit 821 provides a first pathway for water flow from theupper portion 812 of the vessel 811 to the chemical material held in thelower portion 813 of the vessel 811. The holes 825 in the plate 824provide a second pathway for fluid flow from the lower portion 813 ofthe vessel 811 to the upper portion 812 of the vessel 811. The fluidflowing from the lower portion 813 to the upper portion 812 compriseswater and a portion of the chemical material. In certain embodiments,the insert 820 introduces water to the lower portion 813 of the vessel811 so that the fluid flowing out of the vessel 811 is a moreconcentrated solution. For example, when the insert 820 is part of thesecond container 144 containing an acidic material, the fluid from thesecond container 144 has a higher concentration of acid, so it lowersthe pH level of the water feature faster. Other configurations of theinsert 820 are also compatible with embodiments described herein.

As schematically illustrated in perspective view by FIG. 12, the insertcover 840 comprises a generally rigid cylindrical portion 841 open atone end and configured to fit onto the inner annular ring 826 of theinsert 820. The insert cover 840 further comprises a thin membrane 842across a second end of the insert cover 840 and which covers the upperportion 822 of the tubular conduit 821 and the holes 825 when the insertcover 840 is fit onto the insert 820. In this way, the insert cover 840generally seals the chemical material within the vessel 811 and protectsthe user from exposure to the chemical material before the container 810is installed in the system. In certain embodiments, the insert cover 840is bonded or welded onto the insert 820 such that the insert cover 840is not reversibly removable from the insert 820. In other embodiments,the insert cover 840 is friction fitted onto the insert 820. Otherconfigurations of the insert cover 840 are also compatible withembodiments described herein.

As schematically illustrated in two perspective views by FIGS. 13A and13B, in certain embodiments, the cartridge top 850 comprises a generallycylindrical body 851, a first fluid conduit 852 having a first inlet 852a and a first outlet 852 b, a second fluid conduit 853 having a secondinlet 853 a and a second outlet 853 b, an inner annular ring 854, anouter annular ring 855 having a screw thread 856, a plurality of O-ringrecesses 857 (e.g., three O-ring recesses 857), a key 858, and a handle859. The first inlet 852 a is positioned between a first pair of theO-ring recesses 857, and the second outlet 853 b is positioned between asecond pair of the O-ring recesses 857. In certain embodiments, thefirst pair of O-ring recesses 857 and the second pair of O-ring recesses857 each comprises a common O-ring recess 857, as schematicallyillustrated by FIG. 13B. In other embodiments, the first pair and thesecond pair of O-ring recesses 857 do not have an O-ring recess 857common to both pairs. In certain embodiments, the first fluid conduit852 is an inlet of the cartridge 810 and the second fluid conduit 853 isan outlet of the cartridge 810. Other configurations of the cartridgetop 850 are also compatible with embodiments described herein.

When installed on the vessel 811, the screw thread 856 mates with thescrew thread 815 of the vessel 811, and the gasket 830 is compressedbetween a surface of the cartridge top 850 and the edge surface 814 ofthe vessel 811. In this way, certain embodiments inhibit leakage betweenthe vessel 811 and the cartridge top 850. In certain embodiments, eachcartridge/cartridge top pair has a unique set of screw threads 815, 856.Such embodiments advantageously prevent swapping or installation ofchemical materials into the wrong container. For example, by usingunique screw threads 815, 856 for the first container 134 and the secondcontainer 144, a cartridge 810 containing sanitizing agent can not beinstalled in the second container 144 and a cartridge 810 containingpH-modifying material can not be installed in the first container 134.

In addition, the first outlet 852 b and the second inlet 853 a pressthrough the membrane 842 covering the upper portion 822 of the tubularconduit 821 and the holes 825 of the insert 820, with the first outlet852 a mating with the upper portion 822 of the tubular conduit 821. Inthis way, the assembly of the cartridge 810, the insert 820, and thecartridge top 850 provide a pathway for water flow through the firstfluid conduit 852 of the cartridge top 850, through the tubular conduit821 of the insert 820 into the lower portion of the vessel 811 of thecontainer 810. In addition, the assembly of the cartridge 810, theinsert 820, and the cartridge top 850 provide a pathway for fluid flowfrom the lower portion of the vessel 811, through the holes 825 of theinsert 820, and through the second fluid conduit 853 of the cartridgetop 850.

In certain embodiments, the handle 859 of the cartridge top 850 is usedwhen either removing the cartridge top 850 from the housing 900 orinstalling the cartridge top 850 into the housing 900. In certainembodiments, the handle 859 is an integral portion of the cartridge top850, while in other embodiments, the handle 859 is removable from therest of the cartridge top 850.

FIG. 14 schematically illustrates in perspective view an exemplary firsthousing portion 860 compatible with embodiments described herein. Thefirst housing portion 860 comprises a generally cylindrical body 861open at both ends, a first fluid conduit 862, a second fluid conduit863, a key notch 864, an inner surface 865, and a ridge 866.

In certain embodiments, the second housing portion 880 comprises agenerally cylindrical body 881 open at both ends, as schematicallyillustrated by FIG. 15A. The generally cylindrical body 881 fits withthe first housing portion 860 and contacts the ridge 866 of the firsthousing portion 860. In certain embodiments, the end portion 890comprises a generally cylindrical body 891 open at one end 892 andclosed at the other end 893, as schematically illustrated by FIG. 15B.The end portion 890 fits onto the second housing portion 880. Onceassembled in certain embodiments, the first housing portion 860, thesecond housing portion 880, and the end portion 890 form the housing 900into which the cartridge 810 is installed. Other configurations of thefirst housing portion 860, the second housing portion 880, the endportion 890, and the housing 900 are also compatible with embodimentsdescribed herein.

In certain embodiments, the first housing portion 860, the secondhousing portion 880, and the end portion 890 each comprise a plasticmaterial (e.g., polyvinyl chloride or PVC). The outer diameter of thesecond housing portion 880 in certain embodiments is approximately 2.5inches. Both the first housing portion 860 and the end portion 890 aresealed onto the second housing portion 880 using an adhesive (e.g.,solvent cement).

In certain embodiments, the housing 900 formed by the first housingportion 860, second housing portion 880, and end portion 890advantageously provides secondary containment to prevent chemicalmaterial from leaking out of the cartridge and out of the container.Certain such embodiments advantageously isolate other equipment of thewater feature from any chemical materials leaking from the cartridge810, thereby preventing corrosion. In certain embodiments, the housing900 is mountable to a bracket or flange in proximity to the waterfeature for easy access.

In certain embodiments, when the cartridge top 850 is installed in thefirst housing portion 860, a lower portion of the cartridge top 850contacts the ridge 866 to facilitate correct positioning of thecartridge top 850 in the first housing portion 860. The cartridge top850 is configured to fit in the first housing portion 860 with theplurality of O-rings 870 positioned in the plurality of O-ring recesses857. The O-rings 870 are compressed by the inner surface 865 of thefirst housing portion 860, thereby providing generally sealed annularregions between the O-rings 870. For example, for three O-rings 870 inthe three O-ring recesses 857 shown in FIGS. 13A and 13B, two generallysealed annular regions are formed with the first inlet 852 a is in oneof the generally sealed annular regions and the second outlet 853 b in adifferent generally sealed annular region. In this way, the O-rings 870fluidly isolate the first inlet 852 a and the second outlet 853 b fromone another. In addition, the O-rings 870 fluidly isolates the outsideof the housing 900 from the secondary containment area formed by thefirst housing portion 860, the second housing portion 880, and the endportion 890, thereby inhibiting fluid leakage.

The key 858 of the cartridge top 850 fits into the key notch 864 of thefirst housing portion 860, thereby fixing a relative orientation of thecartridge top 850 with respect to the first housing portion 860. In thisorientation, the first fluid conduit 862 of the first housing portion860 is fluidly coupled with the first inlet 852 a of the cartridge top850, and the second fluid conduit 863 of the first housing portion 860is fluidly coupled with the second output 853 b of the cartridge top850. In certain embodiments, the first fluid conduit 862 and the secondfluid conduit 863 each comprises a tubing fitting configured to becoupled to tubing of the system. In this way, by assembling thecartridge 810, the insert 820, the cartridge top 850, and the firsthousing portion 860, a fluid pathway is formed through the first fluidconduit 862 of the first housing portion 860, through the first fluidconduit 852 of the cartridge top 850, through the tubular conduit 821 ofthe insert 820, to the lower portion 813 of the vessel 811. In addition,the assembly of the cartridge 810, the insert 820, the cartridge top850, and the first housing portion 860 forms a fluid pathway from thelower portion 813 of the vessel 811, through the holes 825 of the insert820, through the second fluid conduit 853 of the cartridge top 850, tothe second fluid conduit 863 of the first housing portion 860.

In certain embodiments, each container 800 has a unique key/key notchpair. Such embodiments advantageously prevent swapping or installationof chemical materials into the wrong container. For example, by usingunique keys 858 and key notches 864 for the first container 134 and thesecond container 144, a cartridge 810 containing sanitizing agent cannot be installed in the second container 144 and a cartridge 810containing pH-modifying material can not be installed in the firstcontainer 134.

In certain embodiments, to replace an old cartridge 810, the user pullsthe handle 859 upward until the cartridge assembly 910 is removed fromthe housing 900. The old cartridge 810 is unscrewed from the cartridgetop 850 and the water remaining in the old cartridge 810 is emptied intothe water feature. In certain embodiments, to install a new cartridge810, a cap on the new cartridge 810 is removed and the cartridge top 850is screwed onto the cartridge 810 in its place. The protrusions of thefirst outlet 852 b and the second inlet 853 a puncture the membrane 842of the cartridge 810, allowing fluid communication with the chemicalmaterial within the cartridge 810. Such embodiments advantageouslyprevent exposure of the user to the chemical material within thecartridge 810. In certain embodiments in which a cartridge 810 isrefilled rather than replaced by a new cartridge 810, the water withinthe cartridge 810 is removed from the cartridge 810 before introducingadditional dry chemical material into the cartridge 810, therebyavoiding overflow of water displaced from the cartridge 810 by the drychemical material.

In certain embodiments in which the container 800 contains dry chemicalmaterial, the incoming water which mixes with the dry chemical materialis advantageously introduced into the bottom of the container 800 and iswithdrawn through the top of the container 800. Such flow pathwaysadvantageously allow dispersion of the dry chemical material and thesolution within the container 800 remains saturated by virtue of theexcess dry chemical material at the bottom of the container 800. As thedry chemical material is consumed, it continues to dissolve until thesolution within the container 800 has a concentration substantially thesame as the concentration in the water feature.

In certain embodiments, the third container 154 comprises a sensor(e.g., conductivity sensor, level switch) which detects the liquid levelin the vessel 811 of the third container 154 and generates a signalindicative of the liquid level. In certain embodiments, the controller120 is responsive to the signal to generate a warning to the user whenthe liquid level is decreased below a predetermined level so that theuser can replace or replenish the third container 154. In certainembodiments, the sensor comprises an electrolytic cell positionedapproximately one inch above the lower portion 823 of the tubularconduit 821, which extends to the lower portion 813 of the vessel 811.Such embodiments provide sufficient safety margin in avoiding calibrantdepletion.

In certain embodiments, the third container 154 which contains theliquid calibrant material is similar to the container 800 describedabove, but without the cartridge 810 and the gasket 830. In certain suchembodiments, the liquid calibrant material is poured directly into thehousing 900. Because the calibrant material is not corrosive, secondarycontainment is not warranted. An exemplary housing 900 compatible withembodiments described herein holds approximately 0.7 liters, which isapproximately equal to the amount of calibrant material used over thecourse of three months with approximately 4 weeks between calibrations.

FIG. 16 schematically illustrates an exemplary container 1000 compatiblewith embodiments in which the chemical material within the container1000 is in liquid form. The container 1000 comprises a collapsiblevessel 1010 (e.g., a compressible bag) which contains the liquidchemical material (e.g., sterilizing agent material, pH-modifyingmaterial, calibrant material) to be introduced into the water feature.The container 1000 further comprises a housing 1020, a first fluidconduit 1030, and a second fluid conduit 1040. The collapsible vessel1010 is within the housing 1020. The first fluid conduit 1030 is fluidlycoupled to the inside of the collapsible vessel 1010, and the secondfluid conduit 1040 is fluidly coupled to the volume defined by theoutside of the collapsible vessel 1010 and the inside of the housing1020.

In certain embodiments, the collapsible vessel 1010 is replaceable suchthat when the chemical material in the vessel 1010 is depleted, thevessel 1010 can be removed and a new vessel 1010 installed in its place.In other embodiments, the vessel 1010 is refillable such that when thechemical material in the vessel 1010 is depleted, the vessel 1010 can beremoved, additional chemical material is placed in the vessel 1010, andthe vessel 1010 is replaced. In still other embodiments, the vessel 1010is refillable without removing the vessel 1010 from the container 1000by introducing replacement chemical material into the vessel 1010through the first fluid conduit 1030.

In certain embodiments, the housing 1020 provides a generally airtightenclosure in which the vessel 1010 is installed. The first fluid conduit1030 provides a pathway for the chemical material to be removed from thevessel 1010. The second fluid conduit 1040 provides a pathway for air orother gas or liquid to enter the housing 1020 surrounding the vessel1010. In certain embodiments, sufficient pressure is provided to the airthrough the second fluid conduit 1040 to allow the chemical material tobe withdrawn from the vessel 1010 through the first fluid conduit 1030(e.g., by suction on the first fluid conduit 1030 or by sufficient airpressure on the second fluid conduit 1040 to force the chemical materialout of the vessel 1010).

Containers compatible with embodiments described herein (e.g.,dry/liquid chemical container 800 or liquid chemical container 1000)store the chemical materials used as sterilizing agents or as acidicmaterial or alkaline material for pH control while advantageouslypreventing corrosive fumes from escaping the container. The mixture ofthese corrosive fumes with the high temperature, high humidity, and poorventilation conditions often found in proximity to water features (e.g.,under the skirt of a spa) would rapidly corrode all exposed metalcomponents.

Sensor Assembly

In certain embodiments, the sensor assembly 110 comprises a pH levelsensor and a sterilizing agent sensor. Exemplary pH sensors compatiblewith embodiments described herein include, but are not limited to, pHsensors with separate reference and pH-sensing electrodes and pH sensorswith a combined reference and pH-sensing electrode. Exemplarysterilizing agent sensors compatible with embodiments described hereininclude, but are not limited to, amperometric sensors, oxidationreduction potential (ORP) sensors, and colorimetry sensors. Exemplaryamperometric sensors compatible with embodiments described herein aredescribed by U.S. Pat. Nos. 6,270,680 and 6,238,555, each of which isincorporated in its entirety by reference herein. Such amperometricsensors can be used to measure the chlorine or bromine concentration inthe water. In certain embodiments, the sensor assembly 110 furthercomprises a temperature sensor, examples of which include, but are notlimited to, thermocouples and thermisters. In certain embodiments, theamperometric sensor can be used as both a sanitizing agent sensor and asa total-dissolved-solid (TDS) sensor.

FIG. 17 schematically illustrates an exploded view of an exemplaryconfiguration of a sensor assembly 110 compatible with embodimentsdescribed herein. In the configuration of FIG. 17, the sensor assembly110 comprises a tee 1110, a first body portion 1120, a second bodyportion 1130, a pH sensor 1140, a printed circuit board 1150, anamperometric working electrode 1160, and an amperometric auxiliaryelectrode 1170.

The tee 1110 of certain embodiments comprises a sensor end 1111 which isconfigured to receive the first body portion 1120, an outlet 1112, aninlet 1113, and a counterbore 1114. The inlet 1113 is configured toreceive water into the sensor assembly 110 and the outlet 1112 isconfigured to output water from the sensor assembly 110. In certainembodiments, the tee 1110 and the first body portion 1120 comprise aplastic or polymer material which are generally resistant to thechemical materials added to the water of the water feature. Exemplarymaterials for the tee 1110 and the first body portion 1120 include, butare not limited to, polyvinyl chloride (PVC) andacrylonitrile-butadiene-styrene (ABS).

In certain embodiments, the sensor assembly 110 is operated in aninverted orientation in which the outlet 1112 of the tee 1110 isgenerally vertical and the inlet 1113 is generally horizontal. In suchan orientation, fluid enters the tee 1110 through the inlet 1113, flowsacross the surfaces of the electrodes 1143, 1144, 1160, 1170, and exitsthe tee 1110 through the outlet 1113. The inverted orientation of thesensor assembly 110 advantageously minimizes the effect of bubbles onthe pH level measurements and/or the sanitizing agent measurements. Incertain embodiments, the higher flow velocity across the surfaces of theelectrodes 1143, 1144, 1160, 1170 compensates for a reduced flow rate ofwater through the tee 1110, thereby enabling operation at flow ratesbetween approximately 5 gallons/hour and approximately 10 gallons/hour.

In certain embodiments, the tee 1110 is removably coupled to a mountingclip 1180 fixedly coupled to an enclosure (not shown). The mounting clip1180 fits around the counterbore 1114 of the tee 1110 so that the tee1110 can be snapped into place in the enclosure.

The first body portion 1120 of FIG. 17 comprises a screw thread 1121configured to reversibly couple to a corresponding screw thread of thetee 1110, and a fixture 1122 configured to reversibly couple to the pHsensor 1140. In certain embodiments, the first body portion 1120 isconfigured to screw into the sensor end 1111 of the tee 1110, forming awaterproof seal. In certain such embodiments, an O-ring (not shown) iscompressed between a surface of the sensor end 1111 and a surface of thetee 1110 to form the waterproof seal.

In certain embodiments, the first body portion 1120 is configured toreceive the printed-circuit board 1150 and to provide electricalcontacts between the printed-circuit board 1150 and the workingelectrode 1160 and the auxiliary electrode 1170. In certain embodiments,the first body portion 1120 has epoxy potting material which is used toprotect the printed-circuit board 1150 from moisture. In certainembodiments, the first body portion 1120 is further configured toreceive a housing cover (not shown), which fits over the first bodyportion 1120 to advantageously provide protection to the pH sensor 1140and the printed-circuit board 1150. In certain embodiments, the housingcover is advantageously removable from the first body portion 1120 topermit removal of the pH sensor 1140 when it is no longer operational,and to permit replacement by a new pH sensor 1140.

The second body portion 1130 of FIG. 17A comprises a sensor tip guardring 1131 and a pair of electrode cavities 1132 configured to receivethe amperometric working electrode 1160 and the amperometric auxiliaryelectrode 1170. The sensor tip guard ring 1131 protects the glass end ofthe pH sensor 1140 from breakage during handling. In certainembodiments, the second body portion 1130 comprises a generallyhydrophobic material, examples of which include, but are not limited to,polyetheretherketon (PEEK), polychlorotrifluorethyene (PCTFE or KEL-F®),and ultra-high molecular weight polyethylene. In certain embodiments,the second body portion 1130 is bonded to the first body portion 1120 byan adhesive (e.g., epoxy, solvent cement).

In certain embodiments, the pH sensor 1140 comprises a combination pHsensor having a pH-sensitive electrode 1143 and a reference junction1144, each of which extends into the water to be measured. In certainembodiments, the pH-sensitive electrode 1143 comprises a glass tubehaving a hydrogen-sensitive end, a pH measuring material (e.g.,potassium chloride and silver chloride having a pH of approximately 7.0)within the glass tube, and a silver wire treated with silver chloridesealed immersed in the pH measuring material. Hydrogen ions in the waterto be measured develop an electrical potential across the pH-sensitiveglass, thereby varying the signal (e.g., in millivolts) from thepH-sensitive electrode. In certain embodiments, the reference junction1144 comprises a porous wick material (e.g., Teflon®, porous ceramic,pelon paper) which electrically couples the water to be measured with areference electrode (not shown) of the pH sensor 1140. The referenceelectrode comprises a silver wire treated with silver chloride sealedinside an inert glass housing and immersed in potassium chloridesaturated with silver chloride. The inert glass housing preventshydrogen ion activity from the water to be measured from influencing theconstant signal (e.g. in millivolts) of the reference electrode.

In certain other embodiments, the pH sensor 1140 has a double-junctionreference electrode with two chambers with a gel material in at leastone chamber. In certain embodiments the reference electrode of the pHsensor 1140 also serves as a reference electrode for an amperometricsensor comprising the working electrode 1160 and the auxiliary electrode1170.

In certain embodiments, the pH sensor 1140 is fixedly sealed in thefirst body portion 1120 forming a waterproof seal using an adhesive,examples of which include, but are not limited to, glue, epoxy, orsolvent cement. In certain other embodiments, the pH sensor 1140 isremovably sealed in the first body portion 1120 to advantageously alloweasy replacement of the pH sensor 1140 once it has reached the end ofits usefulness (e.g., due to depletion of the gelled reference). Incertain such embodiments, an O-ring 1142 is positioned between a surfaceof the pH sensor 1140 and a surface of the first body portion 1120 toform a waterproof seal, and the pH sensor 1140 is held in the first bodyportion 1120 by a reversible mechanism. For example, as schematicallyillustrated by FIG. 17A, the pH sensor 1140 comprises a pin 1141 whichfits into a corresponding cam lock 1123 of the first body portion 1120by twisting the body of the pH sensor 1140 in the fixture 1122. Incertain embodiments, the pin 1141 and cam lock 1123 advantageously alignthe reference junction 1144 between the working electrode 1160 and theauxiliary electrode 1170. Other configurations of the pH sensor 1140 arecompatible with embodiments described herein.

In certain embodiments, the amperometric working electrode 1160 and theamperometric auxiliary electrode 1170 are both electrically conductiveand extend into the water to be measured. In certain embodiments, theworking electrode 1160 and the auxiliary electrode 1170 are eachresistant to the chemical materials (e.g., chlorine, bromine, acidicmaterial, alkaline material) introduced into the water feature.Exemplary materials for the electrodes 1160, 1170 include, but are notlimited to, graphite, glassy carbon, and titanium coated or plated witha conductive material (e.g., platinum) resistant to the chemicalmaterials introduced into the water feature. In certain embodiments, theworking electrode 1160 comprises graphite and the auxiliary electrode1170 comprises a titanium substrate having a platinum plating.

In certain embodiments the working electrode 1160 and the auxiliaryelectrode 1170 are pressed into corresponding recesses 1132 of thesecond body portion 1130 to form an interference fit with a chamfer ofthe second body portion 1130 to form a waterproof seal in the recesses1132. In certain other embodiments, at least one of the workingelectrode 1160 and the auxiliary electrode 1170 are fixedly sealed inthe second body portion 1130 using an adhesive (e.g., glue, epoxy,solvent cement) to form a waterproof seal. In other embodiments, theworking electrode 1160 and the auxiliary electrode 1170 are insertinjection molded to partially encapsulate the electrodes 1160, 1170 intorecesses 1132 of the second body portion 1130. Other configurations ofthe working electrode 1160 and the auxiliary electrode 1170 arecompatible with embodiments described herein.

In certain embodiments, the printed-circuit board 1150 fits into thefirst body portion 1120 and is electrically coupled to the workingelectrode 1160 and the auxiliary electrode 1170 by conductive elementssuch as jumpers, wires, and conductive epoxy. In certain embodiments,the printed-circuit board 1150 comprises a memory device (e.g., anelectrically erasable programmable read-only memory or EEPROM device)which stores information regarding at least one of the pH sensor 1140and the amperometric sensor formed by the printed-circuit board 1150 andthe electrodes 1160, 1170 (e.g., characteristics, calibrationinformation, and/or encryption information). In certain embodiments, theprinted-circuit board 1150 further comprises a temperature sensorcoupled to the circuitry of the printed-circuit board 1150 by aninterface (e.g., an I²C serial interface or an SPI communicationsinterface). Other configurations of the printed-circuit board 1150 arecompatible with embodiments described herein.

Certain embodiments of the sensor assembly 110 utilize a shielded6-conductor cable to connect the printed-circuit board 1150 to thecontroller 120 and a separate shielded cable to connect the pH sensor1140 to the controller 120. Such embodiments which use separate cablesadvantageously allows replacement of the pH sensor 1140 while leavingthe connection between the controller 120 and the amperometric sensorand the temperature sensor undisturbed.

Chemical materials

In certain embodiments, the chemical material added to the water (e.g.,the pH-modifying material or the sanitizing agent material) is in a dryform or is in a liquid form. Examples of dry forms compatible withcertain embodiments described herein include, but are not limited to,water-soluble materials, granular materials, and erodible solidmaterials. In certain embodiments utilizing granular materials, at leasta portion of the dry chemical material remains in an undissolved statewhen saturated by water.

In certain embodiments, the sterilizing agent material contained in thefirst container 134 comprises chlorine or bromine, in either dry orliquid form. Exemplary sterilizing agent materials compatible withembodiments described herein include, but are not limited to, thesubstances listed in Table 1 below, along with some comments on theseexemplary substances. TABLE 1 Sodium Granular; commonly used to sanitizespas; readily dichloroisocyanurate available; easy to handle; pH ofapproximately (“Dichlor”) 6.5. Lithium hypochlorite Not as readilyavailable as dichlor. Calcium hypochlorite Not recommended for spas;widely used and suitable for use in swimming pools. Sodium hypochloriteNot recommended for spas; suitable for use in swimming pools. Trichlortablets Usable with spas or pools; pH of approximately 4, so apH-increasing chemical material is advantageously used with it. Brominetablets Usable with spas or pools; pH-increasing (“BCDMH”) chemicalmaterial may be used instead of acidic material in embodiments in whichthe spa is used heavily.

In certain embodiments, the pH-modifying material contained in thesecond container 144 is acidic, while in other certain embodiments, thepH-modifying material contained in the second container 144 is alkaline.Exemplary alkaline pH-modifying materials compatible with certainembodiments described herein include, but are not limited to, sodiumcarbonate, sodium hydroxide, and sodium bicarbonate. Exemplary acidicpH-modifying materials compatible with certain embodiments describedherein include, but are not limited to, the substances listed in Table 2below, along with some comments on these exemplary substances. TABLE 2Sodium bisulfate Muriatic acid Usable in swimming pools but notrecommended (hydrochloric acid) for spas. Sodium carbonate or Usable forincreasing the pH if an acidic sanitizing sodium bicarbonate agentmaterial is used.

Integrating automatic calibration into a control design includes anumber of challenges with regard to the calibrant material. Calibrantmaterials typically used are excellent breeding grounds for bacteriaunder the-warm environment of a spa or heated pool. The bacteria canchange the pH level of the calibrant material or can cause varioussystem components to clog with biofilms. In addition, the calibrantmaterial preferably does not interfere with the water chemistry of thewater feature. Phosphates commonly used for calibrant materials with apH of 7.0 can be a food source for algae or bacteria, as well as causesevere scaling in the water feature, even at very low levels.

In certain embodiments, cyanuric acid (CYA) is advantageously used asthe calibrant material. CYA exhibits a pKa value of approximately 6.8,making it an excellent choice for a 7.0 pH calibrant material. Inaddition, CYA is commonly used and found in spas using stabilizedchlorine such as dichlor, and does not adversely affect the waterchemistry of the water feature. In certain embodiments, the calibrantmaterial comprises an aqueous solution of cyanuric acid having a pHlevel in a range between approximately 6.0 and approximately 7.5.

Because CYA is an organic compound, bacteria growth can still be aproblem. In certain embodiments, the calibrant material is initiallysuperchlorinated (e.g., at a level of approximately 100 ppm) to kill anymicroorganisms that may be present. After a period of time (e.g., onehour), sodium thiosulfate or H₂O₂ is added to the calibrant material inexcess of the stoichiometry needed to neutralize the chlorine insolution in the calibrant material. The calibrant material is thenpackaged in an opaque, sealed container. In certain other embodiments,the CYA calibrant material is charged with a high level of chlorine toprevent biofilms from forming. Since CYA is a chlorine stabilizer, 50parts-per-million of chlorine will remain in solution for months, if thesolution is protected from light.

In certain other embodiments, biofilms are advantageously prevented byadding a small amount of sodium chloride (NaCl) to the calibrantmaterial and operating a small electrolytic cell placed within the thirdcontainer 154. The chlorine generated in this manner can keep thecalibrant material free of biofilms for a period of a year or more. Incertain embodiments, electrodes typically used for oxygen electrolysisare used in the electrolytic cell. The chloride level of certainembodiments is in a range between approximately 5 milligrams/liter toapproximately 500 milligrams/liter. Other embodiments utilize higherconcentrations of chloride. In certain embodiments, the calibrantmaterial contains between approximately 5 parts-per-million of NaCl andapproximately 10 parts-per-million of NaCl. The chlorine level of such acalibrant material does not exceed these concentrations, such that thecalibrant material advantageously provides a known chlorine level forcalibration of the sanitizing agent sensor. In certain embodiments, theknown chlorine level provides a predetermined sanitizing agent level forcalibration. In certain embodiments, the predetermined sanitizing agentlevel is approximately equal to zero.

Power to the electrolytic cell is applied on a periodic basis toelectrolyze the chloride to chlorine. For example, the electrolytic cellcan be powered daily, every few hours, or every few minutes. In anexemplary embodiment, the electrolytic cell is operated twice a day fora period of 20 minutes each operation. Chlorine generation preferablydoes not occur more often so as to prevent formation of hydroxide duringoperation of the electrolytic cell, which would cause the pH level ofthe calibrant material to rise.

An exemplary calibrant material compatible with embodiments describedherein is a 0.030 mol/liter, pH 7.30 CYA-containing calibrant material.Such a calibrant material is prepared in certain embodiments by addingapproximately 0.868 grams of NaOH to approximately 3.951 grams of CYA,and dissolving both compounds in approximately 1 L of deionized water.In certain embodiments, 5 milligrams/liter of NaCl are added to thecalibrant material. The CYA (98%, Catalog No. 18,580-9 ) and the NaOH(99.99%-semiconductor grade, Catalog No. 30,657-6) are available fromSigma-Aldrich Corp. of Saint Louis, Mo.

In certain embodiments, the electrolytic cell is advantageously used todetect depletion of the calibrant material in the third container 134.Current flowing through the electrolytic cell is measured via a voltagedrop across a serial resistor. When the controller 120 detects that thecurrent level has decreased below a nominal value (e.g., less thanapproximately 0.05 amps), the controller 120 responds by generating asignal indicating that the calibrant material should be replenished. Thecontroller 120 also does not perform any automatic calibration cyclesuntil the condition has been corrected. By not performing automaticcalibration cycles with insufficient amounts of calibrant material,certain such embodiments advantageously avoid erroneous calibrationswhich would otherwise cause erroneous measurements of the pH orsterilizing agent levels.

Controller

In certain embodiments, the controller 120 comprises electroniccircuitry configured to receive signals from the sensor assembly 110 andto transmit control signals to the valve assemblies 132, 142, 152. FIGS.18A-18F schematically illustrate various portions of an exemplarycontroller 120 in accordance with certain embodiments described herein.FIG. 18A schematically illustrates an exemplary microprocessor and otherexemplary control circuitry for the system 400. FIG. 18B schematicallyillustrates an exemplary circuit of a power supply for the system 400.FIG. 18C schematically illustrates an exemplary circuit used forsolenoid control for the first valve assembly 132, the second valveassembly 142, and the third valve assembly 152. FIG. 18D schematicallyillustrates an exemplary circuit used during pH level measurements. FIG.18E schematically illustrates an exemplary circuit used duringsterilizing agent level measurements. FIG. 18F schematically illustratesan exemplary circuit used during total-dissolved-solid levelmeasurements. Other circuitry configurations besides those schematicallyillustrated by FIGS. 18A-18F are also compatible with embodimentsdescribed herein.

The controller 120 of certain embodiments comprises a microprocessorwhich is programmed using software to perform the various actions of thesystem 400. The controller 120 of other embodiments comprises amicroprocessor which is hard-wired to perform the various actions of thesystem 400. In certain embodiments, the microprocessor (labeled U2 inFIG. 18A) is a T89C51AC2 8-bit microcontroller unit available from AtmelCorporation of San Jose, Calif. Persons skilled in the art can selectother microprocessors compatible with embodiments described herein.

In certain embodiments, a pressure switch J12 is responsive to thepressure of the circulation system by sending a corresponding signal tothe microprocessor U2. The microprocessor U2 determines whether thepressure is sufficient for operation of the system 400. In certainembodiments, the pressure switch is a differential pressure switch. Inother embodiments, a flow switch is used in place or in conjunctionwith-the pressure switch. The flow switch is responsive to the waterflow rate of the circulation system by sending a corresponding signal tothe microprocessor U2 which determines whether the flow rate issufficient for operation of the system 400. In certain otherembodiments, the controller 120 comprises a magnetic switch interlockwhich turns off the power to the system 1300 in the event that thesystem 1300 is removed from the water feature.

In certain embodiments, the controller 120 is operable in a plurality ofmodes of operation. In a first mode of operation, the controller 120performs pH level measurements. In a second mode of operation, thecontroller 120 performs sanitizing agent level measurements. In a thirdmode of operation, the controller 120 performs total-dissolved-solidlevel measurements.

When performing pH level measurements, a relay K3 switches the sensorreference to ground and switches the pH-sensitive electrode to a PH-ELEvoltage provided by the circuit schematically illustrated by FIG. 18D.In certain embodiments, the ground of the pH-sensing circuit isselectively decoupled from a system ground and is selectively coupled tothe auxiliary electrode 1170 when performing pH level measurements. Thisselectively decoupling from the system ground in certain embodimentsadvantageously avoids stray currents in the high-impedance pH-sensingcircuit. When performing a sanitizing agent measurement or a TDSmeasurement, the relay K3 switches the sensor reference to a REF-POTvoltage provided by the circuit schematically illustrated by FIG. 18Eand switches the pH-sensitive electrode to ground. In certainembodiments, the pH-sensitive electrode is at ground or zero volts whenthe pH electrode is not in operation so that the corresponding input tothe microprocessor U2 is not floating. In addition, a ground or zerolevel on the pH-sensitive electrode in certain embodiments correspondsto a pH of 7.0, thereby providing a control of whether themicroprocessor U2 is operating correctly.

When performing pH level measurements or when performing TDS levelmeasurements, a relay K1 switches the working electrode 1160 to aTDS-SENSE voltage and the auxiliary electrode 1170 to a TDS-GENERvoltage, where both TDS-SENSE and TDS-GENER are provided by the circuitschematically illustrated by FIG. 18F. For pH level measurements, theworking-electrode 1160 and the auxiliary electrode 1170 are thusAC-coupled to the circuit of FIG. 18E with no DC path that wouldotherwise affect the pH level measurement. When performing a sanitizingagent level measurement, the relay K1 switches the working electrode1160 to a WRK-POT voltage and switches the auxiliary electrode 1170 to aAUX-POT voltage, where both WRK-POT and AUX-POT are provided by thecircuit schematically illustrated by FIG. 18E. In certain embodiments,the relays K3, K1 comprise 5-volt relays which are controlled directlyby I/O pins of the microprocessor U2, and have approximately 22 ohms tolimit the current to approximately 25 milliamps.

System Operation

FIG. 19 schematically illustrates an exemplary system 1300 compatiblewith embodiments described herein. The system 1300 comprises a sensorassembly 110 comprising a pH sensor 1140 and an amperometric sensor1310, a controller 120, a first valve assembly 132, a second valveassembly 142, a third valve assembly 152, a flow sensor 310, and adisplay 1320. The controller 120 is electrically coupled to the pHsensor 1140, the amperometric sensor 1310, the flow sensor 310, thefirst, second, and third valve assemblies 132, 142, 152, and the display1320. The controller 120 receives a pH signal from the pH sensor 1140, asanitizing signal from the amperometric sensor 1310, and a flow ratesignal from the flow sensor 310. The controller 120 transmits controlsignals to the first, second, and third valve assemblies 132, 142, 152and status signals to the display 1320.

In certain embodiments, the display 1320 comprises an alphanumericdisplay (e.g., liquid-crystal display, cathode-ray tube, thin-filmtransistor display), while in other embodiments, the display 1320comprises indicator lights (e.g., incandescent, fluorescent,light-emitting diodes). The display 1320 of certain embodimentscomprises both an alphanumeric display and at least one indicator light.The display 1320 of certain embodiments further comprises buttons,switches, or other input devices electrically coupled to the controller120 and through which the user can control or modify the programming ofthe controller 120. In certain embodiments, the display 1320 is spacedaway from the other components of the system 1300. For example, if thecontroller 120 is installed underneath a spa skirt, the display 1320 canbe coupled to the controller 120 by a communication interface. Incertain other embodiments, the display 1320 is integral with the othercomponents of the system 1300 and is viewable behind an easilyaccessible cover.

FIG. 20A is a flow diagram of an exemplary measurement cycle 1400compatible with embodiments described herein. The cycle 1400 comprisesdetermining if the flow rate is sufficient for operation in anoperational block 1410. If the flow rate is below a predetermined flowrate, then the controller 120 sends a “Flow Rate Failure” status signalto the display 1320. If the flow rate is above the predetermined flowrate, then the controller 120 continues the measurement cycle 1400. Thecycle 1400 further comprises measuring the TDS level in an operationalblock 1420, measuring a pH level in an operational block 1430, measuringa sanitizing agent level in an operational block 1440. If the measuredpH level is above a predetermined value, the cycle 1400 comprises addingpH-modifying material to the water feature in an operational block 1435.If the measured sanitizing agent level is below a predetermined value(e.g., a chlorine level below 1.5 ppm), the cycle 1400 comprises addingsanitizing agent material to the water feature in an operational block1445. In certain embodiments, the system 1300 repeats the cycle 1400 atregular intervals (e.g., every four minutes). Other cycles 1400compatible with embodiments described herein include other operationalsteps or have other sequences of operational steps.

FIG. 20B schematically illustrates an exemplary fluid flow pattern forthe system 1300 when in the measurement mode (e.g., in operationalblocks 1410, 1420, 1430, 1440 of FIG. 20A). The system 1300 comprisesthe sensor assembly 110, controller 120 (not shown in FIG. 20B forclarity), first valve assembly 132, first container 134, second valveassembly 142, second container 144, third valve assembly 152, and thirdcontainer 154. Each of the first, second, and third valve assemblies132, 142, 152 has three valves configured as schematically illustratedby FIG. 5A. The system 1300 further comprises the pressure manifold 210,the vacuum manifold 220, the flow sensor 310 and the venturi tee 320.The system 1300 further comprises a vent 1330 fluidly coupled to thethird valve assembly 152. Other configurations of the system 1300 arealso compatible with embodiments described herein. The directions offluid flow through the system 1300 for the measurement modeschematically illustrated by FIG. 20B are indicated by arrows.

In the measurement mode flow pattern of FIG. 20B, no sterilizing agent,no pH-modifying material, and no calibrant material is currently addedto the water of the water feature. In the flow pattern of FIG. 20B,water flows from the water feature, past the flow sensor 310, throughthe pressure manifold 210, through the first, second, and third valveassemblies 132, 142, 152, through the vacuum manifold 220, through thesensor assembly 110 across the sensor electrodes 1143, 1144, 1160, 1170,and through the venturi tee 320 to return to the water feature. In thisconfiguration, the sensor assembly 110 monitors the sanitization agentlevel and the pH level of the water flowing through the sensor assembly110 and sends corresponding sanitization signals and pH signals to thecontroller 120.

During the measurement mode, the first, second, and third valveassemblies 132, 142, 152 are not energized in certain embodiments. Asdescribed above in relation to FIGS. 6A and 6B, the non-energized first,second, and third valve assemblies 132, 142, 152 close the valvescoupled to the first, second, and third containers 134, 144, 154 andopen the valves which permit water to flow from the pressure manifold210, through the first, second, and third valve assemblies 132, 142,152, to the vacuum manifold 220, as schematically illustrated by FIG.20B.

In the operational block 1420 of FIG. 20, the system 1300 determines ifthe TDS level is above a predetermined level. The TDS level is ofinterest in certain embodiments in which the amperometric sensor 1310needs a minimum TDS level to provide accurate measurements of thesanitizing agent level (e.g., at least approximately 200 ppm of NaCl orat least approximately 400 ppm of NaCl). In certain such embodiments, aninitial salt charge is added to the water to ensure that the TDS levelis above a predetermined level. In certain other embodiments, thesensitivity of the sanitizing agent level measurement of theamperometric sensor 1310 is dependent on the TDS level, as illustratedby Table 3, which gives relative percent deviations of the chlorinesensitivity of an amperometric sensor 1310 for various TDS levels. Incertain embodiments, the controller 120 compensates for variations inthe sensitivity of the amperometric sensor 1310 by using the measuredTDS level and the known sensitivity as a function of the TDS level.TABLE 3 Chlorine sensitivity versus TDS level (in ppm) 200 300 400 6001000 Sensitivity (mV/ppm) 0.603 0.603 0.582 0.582 0.478 Relative PercentDeviation N/A 0% −2% −2% −12%

In certain embodiments, the amperometric sensor 1310 is used to measurethe TDS level. FIG. 21 is a flow diagram of an exemplary processcomprising operational blocks 1501-1514. The process of measuring theTDS level in the operational block 1420 comprises using the circuitryschematically illustrated by FIGS. 18A and 18F to measure the TDS levelusing the amperometric sensor 1310. In certain embodiments, if the TDSlevel is below a first predetermined level (e.g., 200 ppm) as determinedin the operational block 1509, the controller 120 sends a “TDS Problem”error signal to the display 1320 and shuts down the system 1300 in anoperational block 1510. If the TDS level is above a second predeterminedlevel (e.g., 700 ppm or 2000 ppm) as determined in the operational block1511, the controller 120 sends a “Drain Spa” error signal to the display1320 in the operational block 1513. Other processes for measuring theTDS level are compatible with embodiments described herein.

In the operational block 1430 of FIG. 20, the system 1300 measures thepH level. FIG. 22 is a flow diagram of an exemplary process comprisingoperational blocks 1521-1533. The process of measuring the pH level inthe operational block 1430 comprises using the circuitry schematicallyillustrated by FIGS. 18A and 18D to measure the pH level using the pHsensor 1140. In certain embodiments, if a self-test pH level in theoperational block 1521 generates a value that is not substantially equalto 7.0 (e.g., a value which deviates from 7.0 by more than twolowest-significant bits of the controller 120) as determined in theoperational block 1522, the controller sends a “Bad pH Electronics”error signal to the display 1320 in the operational block 1527 and shutsdown the system 1300 in an operational block 1528. Similarly, if themeasured pH level is not within a predetermined range (e.g., between 1and 11) as determined in the operational block 1529, the controller 120sends a “Bad pH Electronics” error signal to the display 1320 in theoperational block 1527 and shuts down the system 1300 in the operationalblock 1528. Other processes for measuring the pH level are alsocompatible with embodiments described herein.

In the operational block 1440 of FIG. 20, the system 1300 measures thesanitizing agent level. FIG. 23 is a flow diagram of an exemplaryprocess comprising operational blocks 1541-1554. The processof-measuring the sanitizing agent level in the operational block 1440comprises using the circuitry schematically illustrated by FIGS. 18A and18E to measure the sanitizing agent (e.g., chlorine) level using theamperometric sensor 1310. In certain embodiments, if the potential ofthe working electrode 1160 is below 0.45 volts as determined in theoperational block 1543 or is above 0.55 volts as determined in theoperational block 1544, the controller 120 sends a “Bad Ref” errorsignal to the display 1320 in the operational block 1545. The system1300 measures the chlorine level using the amperometric sensor 1310 inoperational blocks 1547, 1548, 1549, 1550, converts the reading from theamperometric sensor 1310 into parts-per-million (ppm) in the operationalblock 1551, stores the chlorine level in memory in the operational block1552, and checks the change (or delta) from a previous measurement ofthe chlorine level in an operational block 1553. Other processes formeasuring the sanitizing agent level are also compatible withembodiments described herein.

FIG. 24 is a flowchart of an exemplary process in which the reading fromthe amperometric sensor 1310 is converted into ppm in the operationalblock 1551, which comprises operational blocks 1561-1568. In certainembodiments in which the amperometric sensor 1310 primarily measuresHOCl⁻, and not OCl⁻, a correction factor is applied to adjust for the pHlevel of the water since the equilibrium of the HOCl⁻/OCl⁻dissociationis pH-dependent. For example, since the pKa of chlorine is 7.5, at a pHof 7.5, 50% of the chlorine in the water is in the form of HOCl⁻ and 50%of the chlorine is in the form of OCl⁻. But at a pH of 8.0, only 24% ofthe chlorine will be present as HOCl⁻, with the remainder present asOCl⁻. FIG. 25 is a graph of the HOCl⁻ percentage and the OCl⁻ percentageas a function of pH.

In certain embodiments, the correction factor is included in theprogramming (e.g., software, hardware, or both) of the controller 120.Table 4 lists various values of the [OCl⁻] concentration and the [HOCl⁻]concentration, and the ratio R=[OCl⁻]/[HOCl⁻] for various pH values.TABLE 4 pH [OCl⁻] [HOCl⁻] R 6.60 11.2 88.8 0.126 6.70 13.7 86.3 0.1586.80 16.6 83.4 0.200 6.90 20.1 79.9 0.251 7.00 24.0 76.0 0.316 7.10 28.571.5 0.398 7.20 33.4 66.6 0.501 7.30 38.7 61.3 0.631 7.40 44.3 55.70.794 7.50 50.0 50.0 1.000 7.60 55.7 44.3 1.259 7.70 61.3 38.7 1.5857.80 66.6 33.4 1.995 7.90 71.5 28.5 2.512 8.00 76.0 24.0 3.162 8.10 79.920.1 3.981 8.20 83.4 16.6 5.012 8.30 86.3 13.7 6.310 8.40 88.8 11.27.943 8.50 90.9 9.1 10.000 8.60 92.6 7.4 12.589 8.70 94.1 5.9 15.8498.80 95.2 4.8 19.953 8.90 96.2 3.8 25.119 9.00 96.9 3.1 31.623 9.10 97.52.5 39.811 9.20 98.0 2.0 50.119 9.30 98.4 1.6 63.096 9.40 98.8 1.279.433 9.50 99.0 1.0 100.000To calculate the actual chlorine concentration, the amperometric readingin ppm is divided by the [HOCl⁻] concentration. For example, a pH levelof 7.9 corresponds to a [OCl⁻] concentration of 71.5% and a [HOCl⁻]concentration of 28.5%, and a ratio of 2.512. An amperometric readingbefore correction of 2.00 then corresponds to an actual value of2.0/0.72=2.80 after correction.

FIG. 26 is a flowchart of an exemplary process in which the system 1300checks the delta of the chlorine level measurements in the operationalblock 1553, which comprises operational blocks 1571-1579. In certainembodiments, changes of the chlorine levels are checked repeatedly in amoving box car calculation in an operational block 1571. In the movingbox car calculation, a current chlorine level measurement is compared toprevious chlorine level measurements which were a predetermined numberof measurements previous to the current measurement. If the chlorinelevel drops below a predetermined level (e.g., 1 ppm) as determined inan operational block 1572, the controller 120 checks whether thechlorine level has increased within a first predetermined number ofcycles (e.g., 20) as determined in an operational block 1573. If not,the controller 120 sends a “Fill Chlorine” error signal to the display1320 in an operational block 1576. Furthermore, if the chlorine levelhas not changed within a second predetermined number of cycles (e.g.,360) as determined in the operational block 1577, the controller 120sends a “Chlorine Delta Error” error signal to the display 1320 in anoperational block 1578 and shuts down the system 1300 in an operationalblock 1579.

If the pH level is above a predetermined level (e.g., 7.5), thecontroller 120 sends a “pH High” error signal to the display 1320 andperforms the operational block 1435 in which acidic material is added tothe water feature. In certain embodiments, the controller 120 waits fora predetermined period of time (e.g., four minutes) between cycles inwhich acidic material is added to the water feature. If the pH level isbelow a second predetermined value (e.g., 7.0), the controller 120 sendsa “pH Low” error signal to the display 1320. If the pH level is betweenthe first predetermined level and the second predetermined level, thecontroller 120 sends a “pH OK” status signal to the display 120.

FIG. 27A is a flow diagram of an exemplary process for adding acidicmaterial in the operational block 1435, which comprises operationalblocks 1601-1606. In an operational block 1601, the second valveassembly 142 is energized, and FIG. 27B schematically illustrates theresulting fluid flow pattern for the system 1300. When energized, thesecond valve assembly 142 allows water to flow from the pressuremanifold 210, into the second container 144 to mix with the acidicmaterial contained therein, and to flow out of the second container 144,through the vacuum manifold 220, through the sensor assembly 110 andacross the sensor electrodes 1143, 1144, 1160, 1170, through the venturitee 320, to return to the water feature. In certain embodiments, thesecond valve assembly 142 halts the flow from the pressure manifold 210to the vacuum manifold 220 schematically illustrated by FIG. 20B. Incertain embodiments, the acidic material from the second container 144advantageously flows across the sensor electrodes 1143, 1144, 1160, 1170to remove salt build-up and keep the sensor electrodes 1143, 1144, 1160,1170 clean. In certain other embodiments, a crystal modifier is added tothe water to prevent sensor contamination due to deposits of iron,calcium sulfate, or calcium phosphate from changing the surface of oneor more of the electrodes 1143, 1144, 1160, 1170.

In certain embodiments, the second valve assembly 142 is energized for apredetermined period of time (e.g., 30 seconds). The period of time ofcertain embodiments is variable by the controller 120 to provide more orless acidic material, depending on the pH level measurement. The periodof time of certain embodiments is also variable to take into account thedepletion of the acidic material in the second container 144.

In certain embodiments, the system 1300 monitors the pH level of thefluid coming from the second container 144 to monitor whether the secondcontainer 144 needs to be replaced or replenished. In an operationalblock 1602, the pH level of the fluid flowing from the second container144 is measured. In embodiments in which an acidic material is used asthe pH-modifying material, if the pH level is above a predeterminedlevel (e.g., 5.0) as determined in the operational block 1603, thecontroller 120 sends a “Fill Acid Container” error signal to the display1320 in an operational block 1604. If the pH level is below thepredetermined level as determined in the operational block 1603, thecontroller 120 sends a “Acid OK” signal to the display 1320 in anoperational block 1605. In certain embodiments, the display 1320continues to indicate the error status of the system 1300 until thecondition is corrected (e.g., acidic material is added to the secondcontainer 144 or the second container 144 is replaced, and the pH sensor1140 detects a pH level below the predetermined level).

To ensure that the second container 144 is safe to open and to avoidexposure of the user to residual acid, certain embodiments generate the“Fill Acid Container” signal only when the pH level of the water fromthe second container 144 is approximately equal to the pH level of thewater feature. In certain other embodiments, the controller 120 tracksthe number of cycles in which acidic material is added to the waterfeature to determine whether the acidic material needs to bereplenished. Certain other embodiments utilize a level switch, a floatswitch, a conductivity sensor, or another type of liquid sensor in thesecond container 144 to detect when the acidic material is depleted. Thecontroller 120 responds to the signal indicative of depletion of theacidic material by sending a warning signal to the display 1320 toprompt the user to replace or replenish the second container 144.Certain other embodiments utilize a paddle wheel flow sensor coupled tothe outlet of the second container 144 to monitor the depletion of theacidic material.

If the chlorine level is below a predetermined level (e.g., 2 ppm), thecontroller 120 sends an “Add Chlorine” error signal to the display 1320and performs the operational block 1445 in which chlorine is added tothe water feature. In certain embodiments, the controller 120 waits fora predetermined period of time (e.g., one to four minutes) betweencycles in which acidic material is added to the water feature and cyclesin which chlorine is added to the water feature. This period of timeadvantageously allows the previously-added acidic material to be moreevenly distributed through the water before the addition of the chlorinematerial. If the chlorine level is above a second predetermined value(e.g., 4 ppm), the controller 120 sends a “Chlorine High” error signalto the display 1320. If the chlorine level is between the firstpredetermined level and the second predetermined level, the controller120 sends a “Chlorine OK” status signal to the display 120.

FIG. 28 is a fluid flow pattern for the system 1300 when addingsterilizing agent material to the water feature in the operational block1445. The system 1300 energizes the first valve assembly 132, therebyallowing water to flow from the pressure manifold 210, into the firstcontainer 134 to mix with the sanitizing agent material containedtherein, and to flow out of the first container 134, through the vacuummanifold 220, through the sensor assembly 110 and across the sensorelectrodes 1143, 1144, 1160, 1170, through the venturi tee 320, toreturn to the water feature. In certain embodiments, the first valveassembly 132 also halts the flow of water from the pressure manifold 210to the vacuum manifold 220 schematically illustrated by FIG. 20B. Incertain embodiments, the first valve assembly 132 is energized for apredetermined period of time (e.g., 30 seconds). The period of time ofcertain embodiments is variable by the controller 120 to provide more orless chlorine, depending on the chlorine measurement. The period of timeof certain embodiments is also variable to take into account thedepletion of the sanitizing agent material in the first container 134.In certain embodiments in which dichlor is used as the sanitizing agentmaterial, the chlorine level is adjusted before adjusting the pH levelsince dichlor is slightly acidic and can reduce the need for the acidicmaterial.

In certain embodiments, the system 1300 monitors whether the firstcontainer 134 contains sanitizing agent or whether the first container134 needs to be replaced or replenished. In certain embodiments in whichconcentrated sanitizing agent material will not adversely affect thesensor electrodes 1143, 1144, 1160, 1170 by changing their surfaces orotherwise damaging them, the sensor assembly 110 monitors the sanitizingagent level in the water flowing from the vacuum manifold 220 to theventuri tee 320 while sanitizing agent is being added to the waterfeature. If the sanitizing agent level is below a predetermined level,the controller 120 generates a “Fill Sanitizing Agent” signal which issent to the display 1320. In other embodiments, the controller 120tracks the number of cycles in which sanitizing agent is added to thewater feature to determine whether the sanitizing agent needs to bereplenished. Certain other embodiments, which feed liquid chemicals,utilize a level switch, a float switch, a conductivity sensor, oranother type of liquid sensor in the first container 134 to detect whenthe sanitizing agent material is depleted. In certain embodiments, thecontroller 120 responds to a signal indicative of the depletion of thesanitizing agent material in the first container 134 by sending awarning signal to the display 1320, which prompts the user to replace orreplenish the first container 134. Certain other liquid feed embodimentsutilize a paddle wheel flow sensor coupled to the outlet of the firstcontainer 134 to monitor the depletion of the sanitizing agent material.

In certain embodiments, the system 1300 undergoes an auto-calibrationcycle to check and adjust the calibration of the pH sensor 1140. Theauto-calibration cycle of certain embodiments is performed periodically(e.g., every few weeks, monthly, or in response to measurements by thesensor assembly 120). During the auto-calibration cycle, the sensorassembly 110 is exposed to a calibrant material having a predeterminedpH level (e.g., approximately 7.0 or between approximately 7.0 andapproximately 7.5), and the calibrant material is then discharged intothe water feature.

FIG. 29 schematically illustrates a fluid flow pattern for the system1300 during the auto-calibration cycle. The system 1300 energizes thethird valve assembly 152, thereby allowing a gas (e.g., air) to flowfrom the vent 1330 into the third container 154. In addition, calibrantmaterial is allowed to flow out of the third container 154, through thevacuum manifold 220 and across the sensor electrodes 1143, 1144, 1160,1170, through the venturi tee 320, to the water feature. The air fromthe vent 1330 provides pressure to allow the flow of calibrant materialfrom the third container 154. In certain embodiments, the third valveassembly 152 also halts the flow of water from the pressure manifold 210to the vacuum manifold 220 schematically illustrated by FIG. 20B. Incertain other embodiments in which allowing the calibrant material toenter the water feature may be undesirable, the calibrant material isnot introduced into the water feature, but is discharged to a wasteline.

In certain embodiments, a check valve of the third valve assembly 152between the vent 1330 and the third container 154 advantageouslyprevents excessive exposure of the calibrant material to air, whichcould otherwise degrade the stability of the calibrant material or couldotherwise lead to contamination of the calibrant material bymicroorganisms. In certain embodiments, the system 1300 comprises acheck valve between the outlet of the third container 154 and the thirdvalve assembly 152. This check valve can advantageously prevent backflowand contamination of the calibrant material within the third container154 in the event that the third valve assembly 152 is energized withouta reduced pressure in the vacuum manifold 220 or other systemmalfunction.

In certain embodiments, the third valve assembly 152 is energized for apredetermined period of time (e.g., 15 seconds, 20 seconds, or betweenapproximately 5 seconds and approximately 30 seconds). The period oftime of certain embodiments is variable by the controller 120 to providesufficient calibrant material for the auto-calibration cycle. The periodof time of certain embodiments is also variable to take into account thedepletion of the calibrant material in the third container 154. Incertain embodiments, the third valve assembly 152 is not energized untila predetermined amount of time (e.g., one minute) has elapsed since thelatest addition of acidic material or sanitizing agent material to thewater feature.

In certain embodiments, the system 1300 monitors whether the thirdcontainer 154 contains calibrant material or whether the third container154 needs to be replaced or replenished. In certain embodiments, thecontroller 120 tracks the number of cycles in which calibrant materialis added to the water feature to determine whether the calibrantmaterial needs to be replenished. Certain other embodiments utilize alevel switch, a float switch, a conductivity sensor, or another type ofliquid sensor in the third container 154 to detect when the calibrantmaterial is depleted. Certain other embodiments utilize a paddle wheelflow sensor coupled to the outlet of the third container 154 to monitorthe depletion of the calibrant material. If the calibrant material isbelow a predetermined level, the controller 120 generates a “FillCalibrant” error signal which is sent to the display 1320. The system1300 does not perform an auto-calibration cycle under this errorcondition.

FIG. 30 is a flow diagram of an exemplary auto-calibration cycle 1700compatible with embodiments described herein. In an operational block1710, the calibrant material is introduced to the sensor assembly 110.In an operational block 1720, the pH sensor 1140 measures the pH levelof the calibrant material. In an operational block 1730, the controller120 adjusts a pH offset so that the measured pH level is adjusted toequal the predetermined pH level of the calibrant material (e.g., 7.0).In certain embodiments, after adjusting the calibration of the pH sensor1140, the pH offset is stored in memory. If the pH offset is outside apredetermined range, the controller 120 transmits a “pH Sensor Error”signal to the display 1320 and shuts down the system 1300.

In certain embodiments, a single-point calibration is performed using asingle calibrant material. In certain other embodiments, the system 1300further comprises a fourth container with a second calibrant materialwhich is used to provide an additional calibration point to characterizethe response of the pH sensor 1140 to the pH of the fluid beingmeasured.

The zero or blank level of some sanitizing agent sensors can change overthe life of the sensor, such that the sensor exhibits some current evenwhen no sanitizing agent material is present. This condition can getworse over the lifetime of the sensor due to improper operationaldynamics (e.g., operation of the sensor without fluid flow). This excesscurrent can be interpreted by the controller 120 as a higher sanitizingagent level than is actually present.

Previous calibration schemes for the sanitizing agent sensor have beencumbersome and time-consuming. Chlorine standardizing solutions have alimited shelf life, must be prepared under controlled conditions, andmust be refrigerated until used. Other surrogates, such asiodine/iodate, have previously been used but have stability problems aswell.

In embodiments in which the sanitizing agent sensor and the pH sensor1140 use a common reference electrode, the same changes that occur inthe reference electrode of the pH sensor 1140 also affect the sanitizingagent sensor. In addition, surface changes of the sanitizing agentsensor can change the sensitivity of the sanitizing agent sensor.Therefore, certain embodiments advantageously perform theauto-calibration cycle 1700 in situ. In certain embodiments in which thethird container 154 comprises an electrolytic cell which generateschlorine on a regular basis, the calibrant material is also used tocalibrate the sanitizing agent sensor whenever the pH sensor 1140 iscalibrated.

In certain embodiments, the auto-calibration cycle 1700 furthercomprises calibration of the amperometric sensor 1310, or othersanitizing agent sensor of the system 1300 to correct for changes of thezero level. In an operational block 1740, the amperometric sensor 1310measures the sanitizing agent level of the calibrant material. Inembodiments in which the calibrant material does not contain asignificant concentration of the sanitizing agent material (e.g.,contains no chlorine), the measured chlorine level is used to define azero level for the amperometric sensor 1310. The zero level is thenstored in memory in the operational block 1750 and is used to calculatethe actual chlorine level by subtraction of the zero level from themeasured chlorine level. By performing the auto-calibration cycle 1700at various times, certain embodiments advantageously calibrate thechanging zero level from the measured sanitizing agent level. Certainembodiments advantageously provide chlorine calibration alone, pHcalibration alone, a combination of chlorine and pH calibration, or acombination of chlorine, pH, and TDS calibration.

FIG. 31 schematically illustrates another configuration of the system1300 which allows partial mixing compatible with certain embodimentsdescribed herein. In the configuration of FIG. 31, when the system 1300is adding pH-modifying material to the water feature, there are two flowpaths of water through the system 1300. In a first flow path, waterflows from the water feature, through the flow sensor 310, through thepressure manifold 210, through the first valve assembly 132, through thethird valve assembly 152, through the vacuum manifold 210, through thesensor assembly 210, through the venturi tee 320, to return to the waterfeature. In a second flow path, water flows from the water feature,through the flow sensor 310, through the pressure manifold 210, throughthe second valve assembly 142, into the second container 144 where thewater mixes with the pH-modifying material, out of the second container144, through the second valve assembly 142, through the vacuum manifold220, through the sensor assembly 110, through the venturi tee 320, toreturn to the water feature. In certain embodiments, water flows throughthe first flow path and the second flow path substantiallysimultaneously. Certain such embodiments advantageously allow partialmixing of the water in the second flow path (i.e., water havingpH-modifying material coming from the second container 144) with waterin the first flow path. Other configurations of the system 1300advantageously allow partial mixing of water having sanitizing agentmaterial and water in the first flow path.

FIG. 32 schematically illustrates another configuration of the system1300 which utilizes liquid sanitizing agent material and liquidpH-modifying material. The first container 134 is fluidly coupled to afirst vent 1331 through the first valve assembly 132. The secondcontainer 144 is fluidly coupled to a second vent 1332 through thesecond valve assembly 142. In a manner similar to that described abovein relation to the introduction of liquid calibrant material from thethird container 154 using the third valve assembly 152 and a vent 1330,the system 1300 of FIG. 32 introduces either liquid pH-modifyingmaterial or liquid sanitizing agent material into the water feature.Other configurations are compatible with other combinations of a liquidpH-modifying material, a dry chemical pH-modifying material, a liquidsanitizing agent material, and a dry chemical sanitizing agent material.

In certain embodiments, additional chemical materials may be added tothe water feature in the same manner as described herein. For example inembodiments in which a pH-reducing sanitizing agent material (e.g.,trichlor tablets) is used, a source of soda ash may be introduced usinga source comprising a container having soda ash and a valve assembly.Chemical materials which can be added include, but are not limited to,an alkaline material, a biocide material, an oxidizer material, aclarifier material, an enzyme material, and a fragrance material. Incertain such embodiments, these other chemical materials areadvantageously added to the water feature after the sensor assembly 110to avoid coating or contaminating the sensor electrodes with thesechemical materials.

Certain embodiments described herein advantageously provide at least oneof the sanitizing agent material, the pH-modifying material, and thecalibrant material without the need for pumps or complicated delivermechanisms. Other certain embodiments provide one or more of thefollowing advantages: automatic calibration, use with an ozone venturi,fail-safe operation, no corrosive gases are vented, maintenance-free,unattended operation for months or longer, verification of measurementsfor pH levels and chlorine levels, low cost, simplicity, and use ofequipment already present in many water features, and capable of beingretrofitted to existing water features.

Jetted or whirlpool tubs develop biofilms in the plumbing componentswith repeated use and without performing sanitization. Users aregenerally instructed to add bleach after usage, to circulate the water,and to then drain the tub. However, in practice, few users take the timeto perform this sanitization process. Certain embodiments describedherein can be used to advantageously provide a simple-to-usesanitization process for such tubs. One such embodiment uses a containerfilled with salt and having an electrolytic cell. The container wouldfill by gravity when the tub was filled with water and would immediatelybegin to generate chlorine while the tub was in use. After the userexits the tub, the user would activate a circuit which would open avalve assembly which would allow the chlorine solution to enter theplumbing through one or more of the bath jets. The air line to one jetwould be normally open, then closed during the sanitization process. Thewater would be circulated for a period of time, after which the userwould drain the tub. The use of salt in certain such embodimentsadvantageously provides ease-of-use and advantageously eliminates theneed for handling chemicals.

In certain other embodiments, a two-tube pinch valve system is used witha chlorine container and a timed release following usage. After usage,the user can press a button which would activate a sanitization cyclewhich would release chlorine into the whirlpool bath with thecirculating jets on to sanitize the plumbing. In certain embodiments,the chlorine cycles would increase as the chlorine in the container isdepleted. Certain such embodiments would not have a chlorine sensor,while certain other embodiments would have a chlorine sensor. In anotherembodiment, trichlor tablets are used.

In certain embodiments, a timed control for introducing chemicals intothe water feature is used rather than a response to chemical levels asmeasured by sensors. In certain such embodiments, a cycle for dispensingthe chemical materials into the water is started in response to userinput (e.g., pressing a button). In other embodiments, the cycles arescheduled and performed in response to clock signals. Certain suchembodiments can be used with hot tubs and to dispense various chemicals(e.g., H₂O₂ oxidizer shock and/or biguanide, chlorine, acid). Certainsuch embodiments also comprise an electrolytic cell which can be used toincrease the pH level of the water, since electrolysis in spas generallycauses the pH level to rise.

When used with a swimming pool, certain embodiments utilize the suctionand return ports from a pump rather than from a venturi tee. Thepressure differential of the high and low pressures of the pump serve asthe pressure and vacuum of the embodiments described above. In addition,certain embodiments when used with a swimming pool advantageously use aone-way valve to dispense the pH-modifying material.

Various embodiments have been described herein. Although this inventionhas been described with reference to these specific embodiments, thedescriptions are intended to be illustrative of the invention and arenot intended to be limiting. Various modifications and applications mayoccur to those skilled in the art without departing from the true spiritand scope of the invention as defined in the appended claims.

1-72. (canceled)
 73. A system for automatically maintaining at least oneof a pH level and a sanitizing agent level of water in a water feature,the system fluidly coupled to the water feature, the system comprising:a sensor assembly fluidly coupled to the water feature, the sensorassembly responsive to at least one of a pH level of the water and asanitizing agent level of the water, the sensor assembly responsive tothe pH level by generating a pH signal corresponding to the pH level,the sensor assembly responsive to the sanitizing agent level of thewater by generating a sanitization signal corresponding to thesanitizing agent level; a controller operatively coupled to the sensorassembly, the controller generating control signals in response to atleast one of the pH signal and the sanitization signal; at least one ofa first source and a second source, the first source comprising a firstvalve assembly and a first container containing an sanitizing agentmaterial, the first valve assembly responsive to at least a portion ofthe control signals from the controller by selectively allowing thesanitizing agent material to flow from the first container to the waterfeature,the second source comprising a second valve assembly and asecond container containing a pH-modifying material, the second valveassembly responsive to at least a portion of the control signals fromthe controller by selectively allowing the pH-modifying material to flowfrom the second container to the water feature; and a third sourcecomprising a third valve assembly and a third container containing aliquid calibrant material, the third valve assembly responsive to atleast a portion of the control signals from the controller byselectively allowing the calibrant material to flow from the thirdcontainer through the sensor assembly to the water feature.
 74. Thesystem of claim 73, wherein the sanitizing agent material is a drychemical, and the first valve assembly selectively allows water to flowfrom the water feature into the first container, to mix with thesanitizing agent material, and to return to the water feature.
 75. Thesystem of claim 73, wherein the sanitizing agent material is a liquid.76. The system of claim 75, wherein the first container comprises acollapsible vessel containing the sanitizing agent material.
 77. Thesystem of claim 75, wherein the first valve assembly is fluidly coupledto air, wherein the first valve assembly selectively allows air to flowinto the first container.
 78. The system of claim 73, wherein thesanitizing agent material flows from the first container through thesensor assembly to the water feature.
 79. The system of claim 73,wherein the pH-modifying material is a dry chemical, and the secondvalve assembly selectively allows water to flow from the water featureinto the second container, to mix with the pH-modifying material, and toreturn to the water feature.
 80. The system of claim 73, wherein thepH-modifying material is a liquid.
 81. The system of claim 80, whereinthe second container comprises a collapsible vessel containing thepH-modifying material.
 82. The system of claim 80, wherein the secondvalve assembly is fluidly coupled to air, wherein the second valveassembly selectively allows air to flow into the second container. 83.The system of claim 73, wherein the pH-modifying material is acidic. 84.The system of claim 73, wherein the pH-modifying material is alkaline.85. The system of claim 73, wherein the pH-modifying material flows fromthe second container through the sensor assembly to the water feature.86. The system of claim 73, further comprising: a pressure manifoldfluidly coupled to the water feature, the first valve assembly, and thesecond valve assembly; and a vacuum manifold fluidly coupled to thefirst valve assembly, the second valve assembly, the third valveassembly, and the sensor assembly.
 87. The system of claim 86, whereinthe first valve assembly is fluidly coupled to the second valveassembly, and the second valve assembly is fluidly coupled to the thirdvalve assembly, wherein each of the first valve assembly, the secondvalve assembly, and the third valve assembly is responsive to at least aportion of the control signals from the controller by allowing water toflow from the pressure manifold, through the first, second, and thirdvalve assemblies, to the vacuum manifold.
 88. The system of claim 87,wherein the first valve assembly has a first state in which water isallowed to flow from the pressure manifold into the first container andout to the vacuum manifold, and wherein the first valve assembly has asecond state in which water is allowed to flow from the pressuremanifold to the second valve assembly.
 89. The system of claim 88,wherein the first valve assembly is responsive to at least a portion ofthe control signals by switching between the first state and the secondstate.
 90. The system of claim 87, wherein the second valve assembly hasa first state in which water is allowed to flow from the pressuremanifold into the second container and out to the vacuum manifold, andwherein the second valve assembly has a second state in which water isallowed to flow from the first valve assembly to the third valveassembly.
 91. The system of claim 90, wherein the second valve assemblyis responsive to at least a portion of the control signals by switchingbetween the first state and the second state.
 92. The system of claim91, wherein the third valve assembly has a first state in whichcalibrant material is allowed to flow from the third container to thevacuum manifold and water is not allowed to flow from the second valveassembly to the vacuum manifold, and wherein the third valve assemblyhas a second state in which calibrant material is not allowed to flowfrom the third container to the vacuum manifold and water is allowed toflow from the second valve assembly to the vacuum manifold.
 93. Thesystem of claim 92, wherein the third valve assembly is responsive to atleast a portion of the control signals by switching between the firststate and the second state.
 94. The system of claim 86, furthercomprising a flow switch fluidly coupled to the water feature and to thepressure manifold, the flow switch responsive to a flow rate from thewater feature to the pressure manifold by generating a flow signalindicative of the flow rate, the controller responsive to the flowsignal.
 95. The system of claim 86, wherein the vacuum manifold isfluidly coupled to the water feature through the sensor assembly. 96.The system of claim 73, further comprising a venturi tee through whichwater of the water feature flows, the sensor assembly fluidly coupled tothe venturi tee.
 97. A sanitization system for automatically controllingthe pH level and sanitizing agent level of a water feature, thesanitization system comprising: a water circulation system in fluidcommunication with the water feature; a sanitizing agent source in fluidcommunication with the water circulation system, the sanitizing agentsource comprising a sanitizing agent material; a pH-modifying materialsource in fluid communication with the water circulation system, thepH-modifying material source comprising a pH-modifying material; asanitizing agent sensor including a probe in fluid contact with water inthe water circulation system, the sanitizing agent sensor generating asanitizing agent output signal indicative of a sanitizing agent level inthe water; a pH sensor including a probe in fluid contact with the waterin the water circulation system, the pH sensor generating a pH outputsignal indicative of a pH level in the water; a calibrant materialsource in fluid communication with at least one of the sanitizing agentsensor and the pH sensor, the calibrant material source comprising acalibrant material having at least one of a predetermined pH level and apredetermined sanitizing agent level; and a control system responsive tothe sanitizing agent output signal by selectively switching thesanitizing agent source between an active state in which the sanitizingagent source adds sanitizing agent material to the water and an inactivestate in which the sanitizing agent source does not add sanitizing agentmaterial to the water so as to maintain the sanitizing agent levelwithin a first preset range, the control system further responsive tothe pH output signal by selectively switching the pH-modifying materialsource between an active state in which the pH-modifying material sourceadds pH-modifying material to the water and an inactive state in whichthe pH-modifying material source does not add pH-modifying material tothe water so as to maintain the pH level within a second preset range,the control system further configured to recalibrate at least one of thesanitizing agent output signal and the pH output signal by selectivelyswitching the calibrant material source between an active state in whichthe calibrant material source introduces calibrant material to at leastone of the sanitizing agent sensor and the pH sensor and an inactivestate in which the calibrant material source does not introducecalibrant material to at least one of the sanitizing agent sensor andthe pH sensor.
 98. The sanitization system of claim 97, wherein thecontrol system calibrates the sanitizing agent output signal received bythe control system to be indicative of the predetermined sanitizingagent level while the calibrant material source is in the active state.99. The sanitization system of claim 98, wherein the predeterminedsanitizing agent level is approximately equal to zero.
 100. Thesanitization system of claim 97, wherein the control system recalibratesthe pH output signal received by the control system to be indicative ofthe predetermined pH level while the calibrant material source is in theactive state.
 101. The sanitization system of claim 97, furthercomprising a pressure differential source that maintains a pressuredifferential between an inlet and an outlet of the sanitizing agentsource when the sanitizing agent source is in the active state, thepressure differential causing water to enter the sanitizing agent sourcethrough the inlet, to mix with the sanitizing agent material, and toleave the sanitizing agent source through the outlet.
 102. Thesanitization system of claim 97, further comprising a pressuredifferential source that maintains a pressure differential between aninlet and an outlet of the pH-modifying material source when thepH-modifying material source is in the active state, the pressuredifferential causing water to enter the pH-modifying material sourcethrough the inlet, to mix with the pH-modifying material, and to leavethe pH-modifying material source through the outlet.
 103. Thesanitization system of claim 97, wherein the calibrant materialintroduced to at least one of the sanitizing agent sensor and the pHsensor flows into the water feature.
 104. A system for measuring achemical level of water in a water feature, the system fluidly coupledto the water feature, the system comprising: a sensor assembly fluidlycoupled to the water feature, the sensor assembly responsive to thechemical level of the water by generating a signal corresponding to thechemical level; a controller operatively coupled to the sensor assembly,the controller using a calibration function to calculate the chemicallevel in response to the signal generated by the sensor assembly, thecontroller generating a calibrant control signal; and a calibrant sourcecomprising a calibrant material, the calibrant source responsive to thecalibrant control signal from the controller by selectively allowing thecalibrant material to flow from the calibrant source to the sensorassembly, wherein the controller calculates the calibration functionwhile the calibrant material flows from the calibrant source to thesensor assembly.
 105. The system of claim 104, further comprising asource of a chemical material, the source responsive to a source controlsignal from the controller by selectively allowing the chemical materialto flow from the source into the water of the water feature, wherein thecontroller generates the source control signal in response to the signalcorresponding to the chemical level.
 106. The system of claim 104,wherein the chemical level is a sanitizing agent level, the chemicalmaterial is a sanitizing agent material, and the sensor assembly isresponsive to the sanitizing agent level of the water.
 107. The systemof claim 104, wherein the chemical level is a pH level, the chemicalmaterial is a pH-modifying material, and the sensor assembly isresponsive to the pH level of the water.
 108. The system of claim 107,wherein the pH-modifying material is acidic.
 109. The system of claim107, wherein the pH-modifying material is alkaline.
 110. The system ofclaim 104, wherein the calibrant material flows from the sensor assemblyto the water feature.
 111. The system of claim 104, wherein thecalibrant source comprises a sensor which generates a signal indicativeof an amount of calibrant material in the calibrant source.
 112. Thesystem of claim 104, wherein the calibrant source comprises a sensorwhich generates a signal indicative of an amount of calibrant materialwhich flows out of the calibrant source.
 113. The system of claim 112,wherein the sensor comprises a flow sensor.
 114. The system of claim104, wherein the calibrant material comprises an aqueous solution ofcyanuric acid having a pH level in a range between approximately 6.0 andapproximately 7.5.